Patent Publication Number: US-2004050446-A1

Title: Twisting apparatus of electric wires

Description:
BACKGROUND OF THE INVENTION  
       [0001] 1. Field of the Invention  
       [0002] This invention relates to a twisting apparatus for twisting a pair of electric wires.  
       [0003] 2. DESCRIPTION OF THE RELATED ART  
       [0004] A cable for transmission of signal generally has a pair of electric wires that are twisted to suppress an influence of noise and to reduce an attenuation of the signal.  
       [0005] U.S. Pat. No. 5,946,897 and FIG. 11 herein both show a first known twisting apparatus of electric wires. The apparatus shown in FIG. 11 is used by holding first and second ends of electric wires W 1  and W 2  with electric wire clamps A and B. The process continues by rotating the one electric wire clamp A with a driving source C including an electric motor to twist the first ends of the electric wires W 1  and W 2  while maintaining the other electric wire clamp B in a stationary state. Thus, the apparatus shown in FIG. 11 is operative for twisting the electric wires W 1  and W 2 .  
       [0006] The twisting apparatus of FIG. 11 secures the second (left) ends of the electric wires W 1  and W 2  to the electric wire clamp B. The first (right) ends of the electric wires are held by the electric wire clamp A and are rotated. Thus, the electric wires W 1  and W 2  are twisted together. If the electric wires W 1  and W 2  have a large diameter, a high recovery force is exerted in the twisted electric wires after twisting. This high recovery force tends to spread out and untwist the electric wires W 1  and W 2 . To avoid such problem, the electric wires W 1  and W 2  are distorted by twisting them at pitches more than desired pitches. Then, the electric wire clamp A is rotated in a reversed direction by the additional number of twisting to prevent the above-described untwisting. However, this construction will cause uneven pitches in the twisted electric wires W 1  and W 2  and form clearances between them.  
       [0007] Japanese Patent Public Disclosure No. 2001-319536 and FIG. 12 herein both show a second known twisting apparatus of electric wires. The apparatus shown in FIG. 12 is used by holding first ends of a pair of electric wires W 1  and W 2  with a holding unit a and holding the second ends of the electric wires W 1  and W 2  with a holding unit p so that each second end is not fixed, is but restrained from rotating together with the other. The process continues by rotating the holding unit a by a driving source C including an electric motor to twist the first ends of the electric wires W 1  and W 2 . Then, the whole length of the electric wires W 1  and W 2  are twisted together.  
       [0008] The twisting apparatus of FIG. 12 fixes the second (left) ends of the electric wires W 1  and W 2 , but allows the wires W 1  and W 2  to rotate individually and they are twisted. This apparatus can prevent the untwisting without twisting the first (right) ends of the electric wires W 1  and W 2  at pitches more than the desired pitches. However, there are some holding sections in the electric wire holding units p that cannot restrain the electric wires W 1  and W 2  from moving in an axial direction. In the case where the electric wires W 1  and W 2  have a small diameter and a long length, it is not possible to obtain a tension required for twisting the electric wires W 1  and W 2  in a suitable condition. Consequently, the twisting pitches become uneven. Accordingly, the twisting apparatus of electric wires disclosed in FIG. 12 cannot be applied to the electric wires that have a long length and a small diameter.  
       [0009] In view of the above problems, an object of the present invention is to provide a twisting apparatus of electric wires that can precisely twist electric wires at a constant pitch regardless of their diameter and length.  
       SUMMARY OF THE INVENTION  
       [0010] The invention is directed to a twisting apparatus for electric wires including a first holding unit for holding first ends of a pair of electric wires, a second holding unit for holding second ends of the electric wires, and a twist drive unit for rotating the first holding unit to twist the electric wires. The second holding unit includes a pair of support members that rotate together with the first ends of the electric wires, and a rotary synchronous mechanism that rotates both support members at the same speed and in the same direction by transmitting a rotary force from the one support member to the other support member when the one support member rotates.  
       [0011] According to the above construction, the second ends of the electric wires are allowed to rotate. Thus, it is possible to prevent the second ends from untwisting when the twist drive unit rotates the first holding unit holding the first ends of the electric wires to twist the first ends of the electric wires. The second ends of the electric wires are rotated at the same speed and in the same direction. Thus, a suitable tension is applied to the electric wires upon twisting them and they are twisted properly at a constant pitch.  
       [0012] The second holding unit preferably is provided with a biasing member for biasing both of the support members in directions in which the electric wires are subject to tension stresses. Accordingly the tension stresses are exerted in the electric wires in association with a progress on twisting, and the electric wires are properly twisted.  
       [0013] The invention also is directed to a twisting apparatus of electric wires including a first holding unit for holding first ends of a pair of electric wires, a second holding unit for rotatably holding second ends of the electric wires, respectively, and a twist drive unit for rotating the first holding unit to twist the electric wires. The twisting apparatus of electric wires further comprises: a third holding unit disposed between the first and second holding units for holding the electric wires with each electric wire being allowed to rotate but being restricted from rotating together with the other upon rotation of the first holding unit. A slide drive unit is provided for moving the third holding unit from a start position adjacent the first holding unit to an end position adjacent the second holding unit; and control means is provided for controlling the slide drive unit to move the third holding unit at a speed corresponding to a rotary speed of the first holding unit.  
       [0014] According to the above construction, the third holding unit is moved toward the second holding unit in association with a progress on twisting when the twist drive unit rotates the first holding unit holding the first ends of the electric wires. Thus, the third holding unit can prevent a twisting force exerted in the first ends of the electric wires in the first holding unit from being transmitted to the second ends of the electric wires in the second holding unit. Accordingly, the electric wires are twisted properly at an even pitch.  
       [0015] The foregoing and other features of the invention will become apparent to one skilled in the art to which the present invention relates upon consideration of the invention with reference to the accompanying drawings. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0016]FIG. 1 is a schematic side elevation view of an embodiment of a twisting apparatus of electric wires in accordance with the present invention.  
     [0017]FIG. 2 is a partially broken-away front elevation view of a first holding unit in accordance with the present invention.  
     [0018]FIG. 3 is a partially broken-away plan view of a twist drive unit in accordance with the present invention.  
     [0019]FIG. 4 is a partially broken-away plan view of a second holding unit in accordance with the present invention.  
     [0020]FIG. 5 is a plan view of support members in accordance with the present invention.  
     [0021]FIG. 6 is a front elevation view of the support members in accordance with the present invention.  
     [0022]FIG. 7 is an exploded perspective view of the support members.  
     [0023]FIG. 8 is an explanatory view of a third holding unit in accordance with the present invention.  
     [0024] FIGS.  9 ( a ) and  9 ( b ) are explanatory views of a twisting process of electric wires.  
     [0025]FIG. 10 is a partially broken-away plan view of an alteration of the second holding unit in accordance with the present invention.  
     [0026]FIG. 11 is an explanatory view of a first conventional twisting apparatus of electric wires.  
     [0027]FIG. 12 is an explanatory view of a second conventional twisting apparatus of electric wires. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0028]FIG. 1 shows an embodiment of a twisting apparatus of electric wires in accordance with the present invention. The twisting apparatus of electric wires includes a first holding unit  1  that holds first (right) ends of a pair of electric wires W 1  and W 2 , a second holding unit  2  that holds second (left) ends of the electric wires W 1  and W 2 , a third holding unit  3  that holds intermediate portions of the electric wires W 1  and W 2  between the first and second holding units  1  and  2 . The twisting apparatus further includes a twist drive unit  4  that rotates the first holding unit  1  to twist the electric wires W 1  and W 2 , and a machine frame  5  that supports the units  1  to  4 . The machine frame  5  includes a frame body  6  made of an elongated, lightweight section steel and disposed along the electric wires W 1  and W 2  to be twisted. The frame  5  further includes a plurality of support legs  7 . The frame body  6  has a guide rail (not shown) on which the second and third holding units  2  and  3  slide.  
     [0029] As shown in FIGS. 2 and 3, the first holding unit  1  includes a base plate  8  made of a rectangular plate material. Support brackets  9  are secured to an upper surface of the base plate  8  by bolts, and an operation lever  11  is supported rotatably through a pair of links  10  on the brackets  9 . A clamp arm  12  has a proximal end rotatably supported on the brackets  9  and on a distal end of the operation lever  11 . A clamp plate  14  having a pad element  13  made of urethane rubber is attached to a distal end of the base plate  8 . A reference pin  15  stands on an upper surface of a distal end of the clamp plate  14 .  
     [0030] First ends (right) of the electric wires W 1  and W 2  are disposed on the base plate  8  and clamp plate  14  to interpose the reference pin  15  between the electric wires. The lever  11  then is pushed down from an upper position, shown by a broken line in FIG. 2, to a lower position, shown by a solid line in FIG. 2. The clamp arm  12  is moved down from an upper open position to a lower clamp position. The first ends of the electric wires W 1  and W 2  are pinched between the pad element  13  on the clamp plate  14  and a urethane rubber pad element  16  attached to the lower end surface of the clamp arm  12 .  
     [0031] A rotary shaft  18  is attached through a coupling  17  to a proximal end of the base plate  8 . The rotary shaft  18  is rotatably supported in bearing means  20 , such as ball bearings, provided in a support frame  19  attached to sidewalls of the frame body  6  of the machine frame  5 . A driving force is transmitted from the twist drive unit  4  to the rotary shaft  18  coupled to the base plate  8 . Then, the first holding unit  1  is rotated in the side space along the frame body  6 .  
     [0032] The twist drive unit  4  includes a driven gear  21  having a bevel gear and secured to the rotary shaft  18  of the first holding unit  1 . A drive shaft  23  is supported rotatably in bearings  22  and has ball bearings in the support frame  19 . A drive gear  24  is fixed on the drive shaft  23  and engages the driven gear  21 , and a drive motor  26  is provided for rotating the drive shaft  23  through a coupling member  25 . The drive motor  26  may be a servomotor or the like that is controlled precisely at a variable speed within, for example, 300-1800 rpm (revolution per minute) and at a rotary angle (total amount of revolution) in accordance with a control signal from control means.  
     [0033] As shown in FIG. 4, the second holding unit  2  holds the second (left) ends of the electric wires W 1  and W 2 . The unit  2  includes a pair of supports  27  that rotate together with the second ends of the electric wires W 1  and W 2 . The second holding unit  2  also has a rotary synchronous mechanism  28  that rotates the supports  27  at the same speed and in the same direction. A biasing member  29  biases the supports  27  in a direction in which the electric wires W 1  and W 2  are subject to tension stresses during a twisting of the electric wires W 1  and W 2 , as explained below.  
     [0034] As shown in FIGS.  5  to  7 , each support  27  includes a rotary plate  30  having a rectangular shape in a plan view. A rotary shaft  32  is coupled through a coupling  31  to a proximal end of the rotary plate  30 . The support  27  further includes a slide plate  33  and a compression coil spring  34 . The slide plate  33  can slide along a lower surface of the rotary plate  30  and the compression coil spring  34  pushes the slide plate  33  toward a distal end of the rotary plate  30  and towards a holding position of the electric wires W 1  and W 2 . Two clamps  35  are disposed on an upper end surface of the rotary plate  30  and are coupled to the slide plate  33 .  
     [0035] An intermediate part of the rotary plate  30  has a first pair of guide grooves  36  and  37  that extend in a longitudinal direction and a distal end of the rotary plate  30  has a second pair of guide grooves  38  that extend longitudinally in a reversed V-shape. A distal end of the slide plate  33  has two opposed guide grooves  39  that extend in a width direction (see FIG. 7). Two L-shaped handles  40  and  41  are made of a round bar and project from a proximal end surface of the slide plate  33  (see FIG. 7).  
     [0036] Upper ends of the handles  40  and  41  are inserted upwardly into the first guide grooves  36  and  37  so that the handles  40  and  41  are slidably supported in the first guide grooves  36  and  37 . When the handles  40  and  41  slide in the first guide grooves  36  and  37 , the slide plate  33  slides longitudinally on the lower surface of the rotary plate  30 .  
     [0037] The handle  40  is supported rotatably in the slide plate  33 . An engagement portion  42  is provided in a proximal end of the first guide groove  36  into which the handle  40  is adapted to be inserted. When the upper end of the handle  40  engages the engagement portion  42 , the slide plate  33  is locked on the proximal end of the rotary plate  30  against a pushing force exerted by the compression coil spring  34 . Then, the clamp  35  is kept in a release position, as described below.  
     [0038] A holder  44  is secured to a lower surface of the proximal end of the rotary plate  30 . The holder  44  has a depression  43  in which a second (left) end of the compression coil spring  34  is inserted. The slide plate  33  has a proximal end wall with a depression  45   a  in which a first (right) end of the compression coil spring  34  is inserted. Thus, the slide plate  33  is biased toward the distal end of the rotary plate  30  by the pushing force exerted by the compression coil spring  34  (see FIG. 6).  
     [0039] Each clamp  35  is formed into a block body having a pad element  45  made of urethane rubber on an inner side surface. Drive pins  46  and  47  stand on a lower surface of the clamp  35  to be inserted into one of the second guide grooves  38  in the rotary plate  30 . The drive pins  46  and  47  are arranged in a slanting direction opposed to the second guide groove  38 . The drive pin  46  disposed near the distal end of the rotary plate  30  is longer than the other drive pin  47 . A lower end of the drive pin  46  is inserted into the guide groove  39  in the slide plate  33 .  
     [0040] When the slide plate  33  slides on the lower surface of the rotary plate  30 , the clamps  35  on the upper surface of the rotary plate  30  slide along the second guide grooves  38 . Thus, the clamps  35  move between an approached clamp position to the electric wires W 1  and W 2  shown by a solid line in FIG. 5 and a spaced release position shown by an broken line in FIG. 5.  
     [0041] The handle  40  or  41  can be pulled back so that the slide plate  33  moves to a proximal end of the rotary plate  30  and towards the rotary shaft  32  against the force exerted in the compression coil spring  34 . Thus, the drive pins  46  and  47  slide in the second guide grooves  38  in a rear outer direction. The clamps  35  are guided to move away from each other while retracting. However, the slide plate  33  can be moved toward the distal end of the rotary plate  30  by the pushing force exerted in the compression coil springs  34 . In this situation, the drive pins  46  and  47  slide in the second guide grooves  38  in a front and inner direction. Thus, the clamps  35  are guided to approach each other and press the second ends of the electric wires W 1  and W 2 .  
     [0042] As shown in FIG. 4, the second holding unit  2  has a slide frame  48  that supports the supports  27  rotatably. The slide frame  48  has bearings  49  with ball bearings or the like for rotatably supporting the rotary shaft  32  that is coupled to the rotary plate  30 . Each support  27  rotates about the longitudinal axis of the rotary shaft  32 . Furthermore, the slide frame  48  is supported slidably on a holding frame  50  on the frame body  6 . Thus, the supports  27  of the second holding unit  2  slide on sidewalls of the frame body  6  together with the slide frame  48 .  
     [0043] The slide frame  48  has a rotary synchronous mechanism  28 . The mechanism  28  includes first and second gears  51  and  52  having a pair of spur gears on the rotary shafts  32  of the supports  27 . An intermediate shaft  54  is disposed between the rotary shafts  32 , and intermediate gears  55  are fixed on the intermediate shaft  54 . The intermediate gears  55  engage the first and second gears  51  and  52 , respectively. In the rotary synchronous mechanism  28 , the numbers of teeth of the first and second gears  51  and  52  are equal. If one of the supports  27  rotates during the twisting process of the electric wires W 1  and W 2  described below, a rotating force of the one gear  51  or  52  that rotates together with the one support  27  is transmitted through the intermediate gear  55  to the other gear  51  or  52 . Consequently, the supports  27  are rotated at the same speed and in the same direction.  
     [0044] A biasing member  29  including a tension coil spring is disposed between the holding frame  50  supported on the frame body  6  of the machine frame  5  and the slide frame  48 . The slide frame  48  is biased by the biasing member  29  in a direction in which the frame  48  moves away from the first holding unit  1  during the twisting process of the electric wires W 1  and W 2 , as described below. Consequently, a tension stress is applied to each of the electric wires W 1  and W 2  supported on the support members  27 .  
     [0045] The holding frame  50  is supported slidably on a guide rail (not shown) on the frame body  6  of the machine frame  5  and is restrained from sliding on the guide rail by a lock (not shown). The lock adjusts a locking position of the holding frame  50  on the frame body  6 , namely a position of the second holding unit  2  holding the second ends of the electric wires W 1  and W 2  in accordance with the lengths of the electric wires W 1  and W 2 .  
     [0046] As shown in FIG. 8, the third holding unit  3  includes a slide base plate  56  slidably supported on a guide rail (not shown) on the frame body  6  of the machine frame  5 . A slide bar  57  projects from the slide base plate  56  toward sidewalls of the frame body  6 , and four support bars  58  extend from an upper surface of the slide bar  57 . The electric wires W 1  and W 2  are disposed between a pair of adjacent support bars  58 . The electric wires W 1  and W 2  are allowed to rotate between the first and second holding units  1  and  2  during the twisting process of the electric wires W 1  and W 2 , as described below. When the first holding unit  1  is rotated, the first ends of the electric wires W 1  and W 2  are twisted. The second ends of the electric wires W 1  and W 2  are restrained from rotating together with each other.  
     [0047] A slide drive unit  60  is provided between the slide base plate  56  of the third holding unit  3  and the frame body  6 . The slide drive unit  60  includes, for example, a rack gear  61  extending along the frame body  6 , a pinion gear  62  engaging the rack gear  61 , and a drive motor  63  driving the pinion gear  62 . The drive motor  63  is fixed on the slide base plate  56 . The drive motor  63  is driven to rotate the pinion gear  62  in accordance with a control signal from controller  64  contained in a control box. The slide base plate  56  of the third holding unit  3  moves at a constant speed from a start position near the first holding unit  1  to an end position near the second holding position  2  in synchronization with rotation of the first holding unit  1 .  
     [0048] The drive motor  63  may be a servomotor or the like in which a rotary speed is varied and a rotary angle (total amount of revolution) is controlled in accordance with a control signal from the controller  64 . The controller  64  has a function of operating and setting a sliding speed of the slide base plate  56  (revolution speed of the drive motor  56 ) in accordance with a twisting number of the electric wires W 1  and W 2  from input means  65 , namely a revolution number of the first holding unit  1  and a twisting length over a whole length of the electric wires W 1  and W 2 . For example, in the case where the first holding unit  1  is rotated by 40 revolutions and the electric wires W 1  and W 2  having a twisted length of 1000 mm are provided with 40 twisted portions, the rotary speed of the drive motor  63  is set to displace the third holding unit  3  by a distance of 25 mm during one revolution of the first holding unit  1 .  
     [0049] In the case where the twisting apparatus is used for twisting the electric wires W 1  and W 2 , as shown in FIG. 9( a ), the third holding unit  3  is moved to a start position adjacent the first holding unit  1 . The operation lever  11  of the first holding unit  1  then is actuated to set the clamp arm  12  to the upper open position (see the broken line in FIG. 2). The first ends of the electric wires W 1  and W 2  are guided onto the base plate  8  through a space between the support bars  58  of the third holding unit  3  to interpose the reference pin  15  between the first ends of the electric wires W 1  and W 2 . The operating lever  11  then is actuated, and the clamp arm  12  is moved down to the clamp position. The first holding unit  1  clamps the first ends of the electric wires W 1  and W 2  (see the solid line in FIG. 2 and FIG. 3).  
     [0050] The handles  40  and  41  on the supports  27  of the second holding unit  2  are disposed beforehand at a position corresponding to the length of the electric wires W 1  and W 2 . The handles  40  or  41  of the supports  27  then are actuated, and the clamps  35  are locked at the spaced position and the second ends of the electric wires W 1  and W 2  are guided into a space between the clamps  35 . The handles  40  then are released from the engagement portions  42  and the clamps  35  are moved to the clamp position. The second holding unit  2  clamps the second ends of the electric wires W 1  and W 2 .  
     [0051] A start button (not shown) is turned on, and the drive motor  26  of the twist drive unit  4  begins driving. As a result, the base plate  8  of the first holding unit  1  is rotated to twist the first ends of the electric wires W 1  and W 2 . As shown in FIGS. 8 and 9( b ), the drive motor  63  of the slide drive unit  60  is actuated while twisting the electric wires W 1  and W 2  between the first holding unit  1  and the third holding unit  3 . The third holding unit  3  is moved from the start position near the first holding unit  1  to the end position near the second holding unit  2  at a constant speed as the twisting process progresses.  
     [0052] The twisting process of the electric wires W 1  and W 2  is finished when the drive motor  26  of the twist drive unit  4  rotates the base plate  8  of the first holding unit  1  by a predetermined total number of revolutions. The twist drive unit  4  and slide drive unit  60  automatically stop driving when the third holding unit  3  reaches the end position. Thereafter, the first and second holding units  1  and  2  release the first and second ends of the electric wires W 1  and W 2  and the twisted wire is removed from the twisting apparatus. The third holding unit  3  then is returned to the start position, and new electric wires W 1  and W 2  are set on the twisting apparatus. The above steps then are repeated.  
     [0053] The length of the electric wires W 1  and W 2  and the number of twists could be changed on account of a change of a kind of electric wires W 1  and W 2  to be set. Thus, the input means  65  input data such as the length of the electric wires W 1  and W 2  and the number of twists into the control means  64 . The set position of the second holding unit  2  is changed in accordance with a twisting length of new electric wires W 1  and W 2 , and the new electric wires W 1  and W 2  are set on the twisting apparatus.  
     [0054] As described above, the invention is directed to a twisting apparatus of electric wires including the first holding unit  1  for holding the first ends of the pair of electric wires W 1  and W 2 , the second holding unit  2  for holding the second ends of the electric wires W 1  and W 2 , and the twist drive unit  4  for rotating the first holding unit  1  to twist the electric wires W 1  and W 2 . The second holding unit  2  includes the pair of support members  27  that rotate together with the first ends of the electric wires W 1  and W 2 , and the rotary synchronous mechanism  28  that rotates both support members  27  at the same speed and in the same direction by transmitting a rotary force from the one support member  27  to the other support member  27  when the one support member  27  rotates. Accordingly, the electric wires can be twisted precisely at a constant pitch regardless of their diameter and length.  
     [0055] That is, the second (left) ends of the electric wires W 1  and W 2  are rotatably held by the second holding unit  2 . Thus, it is possible to prevent the twisted wire from being untwisted by a high recovery force, even if diameters of the electric wires W 1  and W 2  are great in size. Accordingly, it is not necessary to twist the electric wires W 1  and W 2  at pitches more than desired, and it is possible to twist the electric wires W 1  and W 2  precisely at a proper pitch.  
     [0056] The first ends of the electric wires W 1  and W 2  are rotated to carry out the twisting process, and a torsion force exerted in the electric wires W 1  and W 2  is transmitted to the second ends of the electric wires W 1  and W 2  to rotate them. A rotary force exerted in one of the electric wires W 1  and W 2  then is transmitted through the rotary synchronous mechanism  28  to the other. The electric wires W 1  and W 2  are rotated at the same speed and in the same direction. Accordingly, it is possible to prevent an unbalance, such as an excessive twisting, in only one of the electric wires W 1  and W 2 . Consequently, it is possible to prevent one of the electric wires W 1  and W 2  from untwisting more than the other. It is also possible to prevent formation of clearances between the electric wires W 1  and W 2  due to the disturbance of twisting.  
     [0057] The supports  27  of the second holding unit  2  and the rotary synchronous mechanism  28  serve as a weight that applies a tension to the electric wires W 1  and W 2  when electric wires W 1  and W 2  with a small diameter are twisted. This can twist the electric wires W 1  and W 2  properly with the electric wires W 1  and W 2  being tensioned over the entire length. Accordingly, even if the electric wires W 1  and W 2  have small diameters, it is possible to set a twisting pitch precisely and closely.  
     [0058] The biasing member  29  on the second holding unit  2  biases the supports  27  in a direction in which the electric wires W 1  and W 2  are subject to tension stresses. The tension applied to the electric wires W 1  and W 2  by the biasing member  29  enables a twisting pitch to be set more precisely and closely. As the twisting process of the electric wires W 1  and W 2  progresses, the supports  27  supporting the second ends of the electric wires W 1  and W 2  are pulled toward the first holding unit  1  in connection with the progress on the twisting process, thereby increasing the biasing force of the biasing member  29 . Accordingly, when the electric wires W 1  and W 2  are twisted at the finishing stage of the twisting process, that is, at a position away from the first holding unit  1  that applies a torsion force to the electric wires W 1  and W 2 , it is possible to suppress the disturbance of twisting.  
     [0059] As described above, the twisting apparatus of electric wires includes the first holding unit  1  for holding the first ends of the electric wires W 1  and W 2 , the second holding unit  2  for rotatably holding the second ends of the electric wires W 1  and W 2 , respectively, and the twist drive unit  4  for rotating the first holding unit  1  to twist the electric wires W 1  and W 2 . The twisting apparatus of electric wires further comprises the third holding unit  3  between the first and second holding units  1  and  2  for holding the electric wires W 1  and W 2  such that each of the electric wires is allowed to rotate but is restricted from rotating together with the other electric wire upon rotation of the first holding unit  1 . Additionally, the slide drive unit  60  moves the third holding unit  3  from the start position adjacent the first holding unit  1  to the end position adjacent the second holding unit  2 , and the control means controls the slide drive unit  60  to move the third holding unit  3  at a speed corresponding to a rotary speed of the first holding unit  1 . Accordingly, the third holding unit  3  prevents the twisting force exerted in the first ends of the electric wires W 1  and W 2  by the first holding unit  1  from being transmitted to the second holding unit  2 . Consequently, the invention twists the electric wires W 1  and W 2  evenly and closely.  
     [0060] The third holding unit  3  approaches the first holding unit  1  at the beginning of the twisting process of the electric wires W 1  and W 2 . Therefore, it is possible to twist the electric wires W 1  and W 2  properly and closely within a narrow space between the first and third holding units  1  and  3 . As the twisting process of the electric wires W 1  and W 2  progresses, the third holding unit  3  gradually moves to the downstream side. Since the twisting force for the electric wires W 1  and W 2  can be concentrated at the upstream side from the third holding unit  3 , it is possible to twist the electric wires W 1  and W 2  at a proper and even pitch.  
     [0061] The supports  27  are supported rotatably on the third holding unit  3  so that the supports  27  are rotated in synchronization with each other. However, the second holding unit  2  may have a rotation drive unit that rotates the supports  27  so that the electric wires W 1  and W 2  rotate in a direction opposite from the rotary direction of the first holding unit  1  at a rotary speed corresponding to that of the first holding unit  1  driven by the twist drive unit  4 .  
     [0062] More particularly, as shown in FIG. 10, a rotation drive unit  66  including a servomotor or the like may be provided to rotate one of the rotary shafts  32  coupled to the rotary plates  30  of the supports  27 . As the first ends of the electric wires W 1  and W 2  are twisted when the first holding unit  1  is rotated by the twist drive unit  4 , the rotary plates  30  may be rotated forcedly at the substantially same rotary speed of the first holding unit  1  in a direction in which a torsion of the electric wires W 1  and W 2  is eliminated. Such construction can more effectively suppress the untwisting of the electric wires W 1  and W 2  after twisting electric wires W 1  and W 2  of large diameter.  
     [0063] From the above description of the invention, one skilled in the art will perceive improvements, changes and modifications. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.