METHOD OF AND APPARATUS FOR WINDING COIL ON TOROIDAL CORE

Abstract: A method of and an apparatus suitable for use in winding a coil on a toroidal core of a magnetic head of a video tape recorder or magnetic disc player by passing a wire through a minuscule aperture. The apparatus includes an annular wire guide (11, 11A) formed with a cutout (13), a plurality of pairs of feed rollers (21, 21', 22, 22', 23, 23', 24, 24') having axes disposed perpendicular to a plane in which the annular wire guide (11, 11A) is disposed, the rollers of each pair engaging each other inside the annular wire guide, and at least one core holding unit (6A, 6B) for holding a core (2) in such a manner as to be positioned in the cutout (13) of the annular wire guide (11, 11A). By repeatedly performing the operations of feeding a wire by the feed rollers, guiding the movement of the wire by the annular wire guide (11, 11A) and inserting the wire (1) through a core window of the toroidal core (2) after transporting the wire (1) to the wire insertion position, it is possible to wind a coil positively with increased speed and reliability.

Description: BACKGROUND OF THE INVENTION (1) Field of the Invention This invention relates to methods of and apparatus for winding a coil on a toroidal core, and more particularly it is concerned with a method of and an apparatus suitable for use in winding a coil on a toroidal core of a magnetic head of a video tape recorder (VTR) or magnetic disc player, for example, by passing a wire through a minuscule aperture. (2) Description of the Prior Art One type of apparatus for winding a coil on a toroidal core known in the art is disclosed in Japanese Patent Unexamined Publication No. 186926/83. In this apparatus, a vacuum pipe located beneath a core window is actuated to draw by suction a wire positioned above the core window and pass same through the core window, and then the vacuum pipe is moved downwardly to withdraw and wire and insert same in an inlet, located beneath the core window, of an arcuate guide extending in a direction in which the wire is wound or from beneath to above the core window while a compressed air current is directed against the wire through a nozzle located on a side opposite the wire inlet side of the guide, to thereby feed the wire upwardly through the core window and wind same on the toroidal core. The problem encountered in this apparatus of the prior art is that, since the wire is drawn by suction by means of a vacuum pipe and fed by compressed air while being held by the force of drawn air, difficulty is experienced in ensuring that the wire is positively passed through the core window and also in achieving increased speed of operation. Another type of apparatus for winding a coil on a toroidal core is disclosed in US Patent No. 4,529,138 in which a wire is fed along an annular guide by means of rollers to wind same on the toroidal core, and a portion of the wire is gripped and pulled by a gripper to achieve winding the wire on the toroidal core. This apparatus suffers the disadvantage that the mechanism for winding the wire on the core is complex, thwarting plans to obtain increased speed in operation for winding a wire. Additionally, the apparatus lacks means for avoiding buckling at a leading end portion of the wire and keeping the leading end portion of the wire from entering the inside of the wire guide when the wire is low in stiffness and the core window is small in size. SUMMARY OF THE INVENTION (1) Object of the Invention This invention has as its object the provision of a method of and an apparatus for winding a coil on a toroidal core which enable the production of a toroidal coil to be achieved at high speed and with increased reliability in performance, by repeatedly performing the operation of positively passing the wire through the window of the toroidal core and transporting the leading end portion of the wire to the wire insertion position again and again. (2) Statement of the Invention In one aspect of the invention, the outstanding characteristics enabling the aforesaid object to be accomplished include annular wire guide means formed with a cutout, feed roller means comprising a plurality of pairs of feed rollers, the rollers of each pair engaging each other inside the annular wide guide means and having axes located perpendicular to a plane in which the annular wire guide means is located, and at least one core holding unit for holding a core in such a manner that the window of the core is located inside the cutout of the annular wire guide means. In another aspect of the invention, the outstand­ ing characteractics enabling the aforesaid object to be accomplished include feed roller means imparting tension to the wire, means comprising a pad and a pin for control­ ling the direction in which the wire is tensioned, movable wire guide means located on the wire insertion side of the core window and nozzle means for directing air currents against the wire. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of one example of the core used with a VTR, in which the invention may be incorporated; Fig. 2 is a perspective view of another example of the core used with a magnetic disc player, in which the invention may be incorporated; Fig. 3 is a perspective view of the apparatus for winding a coil comprising a first embodiment of the invention; Fig. 4 is a sectional view taken along the line IV-IV in Fig. 3; Fig. 5 is a sectional view taken along the line V-V in Fig. 3; Figs. 6-11 are views in explanation of the steps of feeding a wire and treating an end portion of the wire and the steps of feeding and discharging a core; Figs. 12-15 are views in explanation of the wire winding step; Fig. 16 is a timing chart showing the relation between the constituent elements of the first embodiment; Fig. 17 is a perspective view of the coil winding apparatus comprising a second embodiment; Fig. 18 is a sectional view taken along the line XVIII-XVIII in Fig. 17; Fig. 19 is a perspective view of the pin drive section of the coil winding apparatus shown in Fig. 17; Figs. 20-28 are views in explanation of the steps of winding a coil in the second embodiment shown in Fig. 17; Fig. 29 is a timing chart showing the relation between the constituent elements of the second embodi­ ment; Fig. 30 is a perspective view of the coil winding apparatus comprising a third embodiment; Fig. 31 is a perspective view, on an enlarged scale, of the wire insertion guide of the third embodi­ ment; Figs. 32 and 33 are views in explanation of the step of winding a coil in the third embodiment; Fig. 34 is a perspective view of the apparatus for winding a coil comprising a fourth embodiment of the invention; Fig. 35 is a sectional view taken along the line XXXV-XXXV in Fig. 34; Fig. 36 is a perspective view of the portion indicated by D in Fig. 34; and Figs. 37-39 are views in explanation of the step of the winding a coil in the fourth embodiment. DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 shows, in a perspective view, one example of the core used with a VTR, in which the invention may be incorporated. The core 2 is a plate-like member formed of ferrite and having a thickness of about 0.4 mm and longitudinal and transverse dimensions of about 2-3 mm. The core 2 comprises a tape sliding surface 2A, a window (hereinafter core window) 3 of about 0.3 x 0.3 mm located in the vicinity of the tape sliding surface 2A and two coil wound portions 4 each located on one of opposite sides of the core window 3 to have an electric wire (hereinafter wire) 1 including a core of about 0.03 mm in diameter wound thereon by passing through the core window 3. The number of turns of the wire 1, which may vary depending on the article to be produced, is usually in the range between 5 and 15 on either one of the two coil wound portions 4. The toroidal core 2 is attached to a forward end of a core base 2B which in turn is mounted to an upper cylinder, not shown. Fig. 2 shows, in a perspective view, one example of the core used with a magnetic disc, in which the invention may be incorporated. The core 2' which is also formed of ferrite includes a head 2C having a thick­ ness of about 0.4 mm and longitudinal and transverse dimensions of about 1-2 mm, and a slider portion 2D having a thickness of about 2 mm and longitudinal and transverse dimensions of about 3-5 mm. A core window 3 of about 0.5 x 0.5 mm is formed in the head 2C of the core 2', and an electric wire 1 including a core of about 0.05 mm in diameter is wound on the coil wound portion 4 located on a side of the core window 3 opposite the side thereof at which the slider portion 2D is located. The number of turns of the wire 1, which may vary depending on the article to be produced, is usually in the range between 10 and 30. Preferred embodiments of the invention will now be described by referring to Figs. 3-39. Fig. 3 shows one embodiment of the apparatus for winding a coil on a toroidal core in conformity with the invention. As shown, the apparatus comprises a core feeding and discharging section 6 in which the core 2 is supported on a base 10 for movement in three directions of Z, X and Y, a coil winding section 7 for winding the wire 1 on the core 2, a wire feeding section 9 for feeding the wire 1 to the coil winding section 7 and a wire trailing end portion withdrawing section 5 for withdrawing a wire trailing end portion 1D in the Z direction from a core holding position. Formed at the top surface of the base 10 in the coil winding section 7 is an annular groove 11A which cooperates with a cover 12 to constitute an annular wire guide 11 formed with a cutout 13. A wire withdrawing rod 90 (or the core 2) is arranged such that opposed side edges of the cutout 13 are disposed on opposite sides of a wire passing hole 90A (or the core window 3 of the core 2) of the wire withdrawing rod 90. A pair of rollers 21 and 21' are located along the annular wire guide 11 in a position which is located on the wire inlet side of the wire passing hole 90A (or the core window 3). A pair of rollers 22 and 22' are located along the annular wire guide 11 in a position which is located on the wire outlet side of the wire passing hole 90A (or the core window 3). A pair of rollers 23 and 23' and a pair of rollers 24 and 24' are located along the annular wire guide 11 in positions which are located between the two pairs of rollers 21, 21' and 22, 22'. The rollers 21, 21', 22, 22', 23, 23' and 24, 24' are located such that their axes of rotation are perpendicular to a plane in which the annular wire guide 11 is located, and the point of contact between the rollers of each pair is disposed inside the annular wire guide 11. A sensor 8 for monitor­ ing the passage of the wire 1 is located on an imaginary straight line connecting the core 2 to the roller 23', and another sensor 8A for monitoring the passage of the wire 1 is located on the bottom surface of a portion of the annular groove 11A between the two pairs of rollers 24, 24' and 21, 21'. Formed at the top surface of the base 10 in the wire feeding section 9 is an arcuate groove 81A which has as its tangent a common tangent of the rollers 21 and 21'. The groove 81A cooperates with the cover 12 for the groove 11A to constitute an arcuate wire guide 81. A cutter 82 is located along the wire guide 81 in a position spaced apart a predetermined distance from the core 2, and rollers 83 and 83' are located on opposite sides of a portion of the wire guide 81 which is spaced apart from the cutter 82 and core 2. A bobbin 84 supported for rotation relative to the base 10 is located in a position spaced apart from the rollers 83, 83', cutter 82 and core 2. The rollers 21, 21', 22, 22', 23, 23', 24, 24' and 83, 83' are controlled to rotate at the same peri­ pheral velocity. The core feeding and discharging section 6 comprises a turntable 85 supported for rotation relative to the base 10, turntable rotating means, not shown and two core holding units 6A and 6B disposed on the turn­ table 85. Each core holding unit 6A (6B) comprises a slider 96A (86B) supported on the turntable 85 for sliding movement in the Y direction, a drive, not shown, for the slider 86A (86B), a core clamper 87A (87B) for clamping the core 2, a gripper 88A (88B) for gripping the trailing end portion 1D and means, not shown, for opening and closing the gripper 88A (88B). Fig. 4 is a sectional view taken along the line IV-IV in Fig. 3, in which the wire end portion withdrawing section 5 comprises a wire withdrawing rod 90 configured to have a forward end portion 90B resembling the core 2 and to be formed with a hole 80A in a position correspond­ ing to that of the core window 3, bearings 91 and 91' secured to the wire withdrawing rod 90, guide rails 92 and 92' engaging the bearings 91 and 91' and secured to the base 10, a rack 93 secured to the wire withdrawing rod 90 and a gear 94 engaging the rack 93 and secured to a shaft 95A of a motor 95 secured to the base 10. By rotating the motor 95, it is possible to move the forward end portion 90B of the wire withdrawing rod 90 from a core holding position shown in solid lines in the figure to a position shown in phantom lines in the figure in which it does not interfere with the core 2 and gripper 88A when the slider 86A moves forwardly. Fig. 5 is a sectional view taken along the line V-V in Fig. 3. A flat surface portion 14 located inside the annular groove 11A on the base 10 is disposed at an elevation lower than that of a flat surface portion 15 located outside the annular groove 11A by a value slightly greater than the diameter of the wire 1. As described previously, the cover 12 is provided to enclose the annular groove 11A. A portion constituted by the groove 11A and cover 12 and a portion constituted by a gap defined between the flat surface portion 14 and cover 12 shall be referred to as a wire guide 11 and a slit 16 respectively. A rotary shaft 30 of the roller 23 is journalled by a bearing 31 for rotation relative to the base 10 and coupled through a coupling 33 to a motor 32 on the base 10. The roller 23' is journalled for rotation by a bear­ ing 36 supported by a shaft 35 secured to a pivotal arm 34 which is pivotally supported by the base 10 and connected to a pneumatic cylinder 39 through a pin 38. By actuating the pneumatic cylinder 39, it is possible to move the pivotal arm 34 in pivoting movement with a pin 37 serving as a fulcrum so as to move the roller 23' from a position in which it presses against the roller 23 to a position shown in phantom lines in Fig. 5 in which it is away from the flat surface portion 14. The rollers 21, 21', 22, 22' and 24, 24' are similar in construction to the rollers 23, 23'. One embodiment of the method of winding a coil on a core in conformity with the invention will be described by referring to Figs. 6-16. Fig. 16 is a timing chart showing the relation between the various constituent elements. Fig. 6 shows the coil winding section 7 and core feeding and discharging section 6 in a condition in which coil winding has been finished. A core 2A on which a coil has been wound is held by the core holding unit 6A disposed in the coil winding section 7. A leading end portion 1E of the wire 1 wound on the core 2A is held between the rollers 23 and 23'. Meanwhile another core 2B is held by the core holding unit 6B and disposed in the core feeding and discharging section 6. A leading end portion 1A of the wire 1 fed from the wire feeding section 9 is held between the rollers 83 and 83' and located in the arcuate wire guide 80. The cutter 82 is in an open position, and the rollers 21', 22', 23' and 24' are forced against the associated rollers 21, 22, 23 and 24 respectively. The wire withdrawing rod 90 is in a lower position. As the slider 86A is moved rearwardly as shown in Fig. 7 from the position shown in Fig. 6, the leading end portion 1E of the wire 1 wound on the core 2A is withdrawn together with the core 2A and released from engagement with the rollers 23, 23', to lie in the slit 16. As the forward end portion 90B of the wire withdrawing rod 90 is moved upwardly to a core holding position simultaneously as the slider 86A is moved rearwardly, the leading end portion 1E of the wire 1 disposed in the core holding position is pushed upwardly by the wire withdrawing rod 90 away from a wire transporting path. Rotation of the rollers 83, 21, 22, 23 and 24 feeds the leading end portion 1A to a position anterior to the core holding position with respect to the direction of movement of the wire 1. Referring to Fig. 8, the leading end portion 1A of the wire 1 is further fed by the rollers 21 and 21' from its position shown in Fig. 7 and guied by the annular wire guide 11 in its movement until it passes through the hole 90A in the wire withdrawing rod 90. With the forward end portion 90B of the wire withdrawing rod 90 being similar in configuration to the core 2, the leading end portion 1A of the wire 1 is able to pass through the hole 90A as is the case with an ordinary coil winding apparatus. The leading end portion 1A of the wire 1 is further fed by the rollers 21, 21', 22, 22', 23, 23' and 24, 24' and guided by the annular wire guide 11, to reach the detector 8A. Upon the leading end portion 1A being sensed by the sensor 8A, the rollers 21, 22, 23, 24 and 83 are caused to stop rotating, the wire 1 is cut by the cutter 82 and the roller 21' is brought out of engagement with the roller 21. The turntable 85 is rotated through 180 degrees. Fig. 9 shows the wire withdrawing rod 90 moved downwardly from its position shown in Fig. 8. Downward movement of the wire withdrawing rod 90 causes the wire trailing end portion 1D inserted in the hole 90A in the rod 90 to be pulled downwardly therefrom. As the slider 86B is moved forwardly to a position shown in Fig. 10 from its position in Fig. 9, the core 2B held by the core holding unit 6B is trans­ ported to the coil winding section 7 and the wire trailing end portion 1D is gripper by the gripper 88B. Fig. 11 shows in a plan view the core 2B located in the core holding position as the slider 86B has moved forwardly. The wire trailing end position 1D is pulled downwardly from the wire outlet side of the core 2B, and the wire leading end portion 1A is disposed in a portion of the annular wire guide 11 between the two pairs of rollers 21, 21' and 24, 24'. The steps of feeding the wire, withdrawing and fixing in place the wire trailing end portion and feeding and discharging the cores have been described. Now let us turn to the step of winding a coil on the core 2B. Fig. 12 shows the rollers 22' and 21' moved from their positions shown in Fig. 11, so that the roller 22' is brought out of engagement with the roller 22 and the roller 21' is brought into engagement with the roller 21 (as indicated by a line B in Fig. 16). An intermediate portion 1B of the wire 1 is fed by the rollers 23 and 23', so that it deviates from the annular wire guide 11 and enters the slit 16. Rotation of the rollers 23 and 23' imparts tension to the intermediate portion 1B of the wire 1 and a wire portion 1C which is already wound on the core 2. At this time, the roller 22' is moved into contact with the roller 22 (as indicated by a line D in Fig. 16). Meanwhile the leading end portion 1A of the wire 1 is fed by the rollers 24 and 24' and guided by the annular wire guide 11 in its movement until it reaches the rollers 21 and 21'. At this time, the roller 24' is brought out of engagement with the roller 24 (as indicated by a line C in Fig. 16). The leading end portion 1A of the wire 1 is further fed by the rollers 21 and 21' and guided by the annular wire guide 11 in its movement until it reaches the wire inlet side of the core window 3. At this time, the intermediate portion 1B of the wire 1 is fed by the rollers 21 and 21', so that it deviates from the annular wire guide 11 and enters the slit 16. The rollers 21', 22', 23' and 24' shown in phantom lines in the figures are indicated to be in a position in which they are out of engagement with the respective associated rollers and away from the flat surface portion 14 shown in Fig. 5. Referring to Fig. 13, the leading end portion 1A of the wire 1 fed from its position shown in Fig. 12 by the rollers 21 and 21' to the cutout 13 is able to pass through the core window 3 without interfering with a wire portion 1C already wound on the coil wound portion 4 of the core 2 because tension is being imparted to the wire portion 1C by the rollers 23 and 23'. The leading end portion 1A does not interfere with the intermediate portion 1B, either, because the latter is being pulled by the rollers 23 and 23' from the coil would portion 4 of the core 2 in a direction opposite the direction of the core window 3. After passing through the core window 3, the leading end portion 1A of the wire 1 is further fed by the rollers 21 and 21' and guided by the annular wire guide 11 in its movement until it reaches the rollers 22 and 22'. Referring to Fig. 14, the sensor 8 senses the passage of the wire 1 from the position shown in Fig. 13, and causes the roller 23' to be disengaged from the roller 23 and moved away from the flat surface portion 14 after lapse of a predetermined period of time. The roller 24' is brought into engagement with the roller 24 (as indicated by a line E in Fig. 16). The intermediate portion 1B of the wire is fed by the rollers 21 and 21', so that a ring formed by the intermediate portion 1B which includes tlhe coil wound portion 4 of the core 2 and the roller 21' has its size reduced and gradually becomes a smaller ring. At this time, the roller 21 is released from engagement with the roller 21 and moved away from the flat surface portion 14 and the roller 23' is brought into engagement with the roller 23 as indicated by a line F in Fig. 16. Meanwhile the leading end portion 1A of the wire 1 is fed by the rollers 22 and 22' and guided by the annular wire guide 11 in its movement, until it reaches the rollers 23 and 23'. Referring to Fig. 15, the leading end portion 1A of the wire 1 is fed from its position shown in Fig. 14 by the rollers 23 and 23' and guided in its movement by the annular wire guide 11, until it reaches the rollers 24 and 24'. Meanwhile the ring formed by the intermediate portion 1B of the wire 1 has its size reduced and biased toward the coil wound portion 4 of the core 2. Referring to Fig. 12 again, the roller 22' is brought out of engagement with the roller 22 and moved away from the flat surface portion 14 from its position shown in Fig. 15. The roller 21' is brought into engagement with the roller 21 again (as indicated by the line B in Fig. 16). The intermediate portion 1B of the wire 1 being fed by the rollers 23 and 23', it enters the slit 16 from the annular wire guide 11. Further rotation of the rollers 23 and 23' imparts tension to the intermediate portion 1B and the portion 1C which is wound already on the coil wound portion 4 of the core 2. Then, the roller 22' is brought into engagement with the roller 22 again (as indicated by the line D in Fig. 16). Meanwhile the leading end portion 1A of the wire 1 is fed by the rollers 24 and 24' and guided in its movement by the annular wire guide 11, until it reaches the rollers 21 and 21'. At this time, the roller 24' is brought out of engagement with the roller 24 and moved away from the flat surface portion 14 (as indicated by the line C in Fig. 16). Further rotation of the rollers 21 and 21' feeds the leading end portion 1A of the wire 1 which is guided in its movement by the annular wire guide 11, until it reaches the wire inlet side of the core window 3. At this time, the intermediate portion 1B of the wire 1 deviates from the wire guide 11 and enters the slit 16 because it is being fed by the rollers 21 and 21'. By performing the operations described herein­ above, one turn of the wire 1 is wound on the core 2. It is possible to produce a coil of the desired number of turns of the wire 1 by repeatedly performing the aforesaid series of operations a predetermined number of times. From the foregoing description, it will be appreciated that the invention enables application of tension to a portion of the wire already wound on the core and transportation of the intermediate portion of the wire in a direction in which it does not interfere with the movement of the leading end portion of the wire to be achieved automatically and continuously, when the leading end portion of the wire is inserted in the core window. This is conducive to an increase in the speed at which coil winding is effected. A second embodiment of the invention will now be described by referring to Figs. 17-29. The apparatus comprising the second embodiment represents improvements in the apparatus comprising the first embodiments shown in Fig. 3 and provides better alignment of the wire in the coil and improved dielectric strength. Fig. 17 is a perspective view of the apparatus for winding a coil comprising the second embodiment, in which a pad 40 supported for vertical movement is located on the wire outlet side of the core 2 inside the annular wire guide 11 of the same construction as shown in Fig. 3 and described by referring to the first embodi­ ment, and a pin 50 supported for vertical and pivotal movements is located inside the annular wire guide 11 in a position substantially diametrically opposed to the core 2. As is the case with the embodiment shown in Fig. 3, the detector 8 for monitoring the passage of the wire 1 is located on an imaginary straight line connecting the core 2 to the roller 23'. Fig. 18 is a sectional view taken along the line XVIII-XVIII in Fig. 17, in which the pad 40 is slidably supported on a vertical shaft 41A of a solenoid 41 supported on the table 10 and forced against the inner surface of the cover 12 by the biasing force of a spring 43 mounted coaxially with the vertical shaft 41A. A pin 42 is forced fitted in the upper end portion of the vertical shaft 41A and extends in a direction perpendicular to the axis of the vertical shaft 41A. As the solenoid 41 is energized to pull the vertical shaft 41A in the Z direction, the pad 40 is moved from the position in which its upper surface is forced against the inner surface of the cover 12 to a position in which its upper surface is spaced apart from the inner surface of the cover 12, as indicated by a phantom line, a distance corresponding to the vertical dimension of the slit 16. Fig. 19 is a perspective view of a drive of the pin 50 shown in Fig. 17, in which the pin 50 is force fitted in an arm 54 rotatably supported by a vertical shaft 59A of a solenoid 59, and one end of a spring 56 mounted concentrically with a projection 64A of the arm 54 is maintained in engagement with the pin 50. An opposite end of the spring 56 is maintained in engagement with a pin 57A force fitted in a plate 57 secured to the vertical shaft 59A of the solenoid 59. The pin 50 is biased upwardly by a spring 55 mounted concentrically with the vertical shaft 59A of the solenoid 59 until a collar 58 fitted around the vertical shaft 59A abuts against the solenoid 59, so that the top of the pin 50 is disposed in a position above the upper level of the slit 16. As the solenoid 59 is energized to pull the vertical shaft 59A in the Z direction, the pin 50 is moved downwardly so that its top is disposed in a position below the lower level of the slit 16, as indicated by a phantom line. A process for winding the wire 1 by using the apparatus shown in Figs. 17-19 will be described by referring to Figs. 20-28. Fig 29 is a timing chart for the operation performed by the apparatus comprising the second embodiment of the invention. Fig. 20 shows the coil winding section in which the wire 1 is wound on the core 2. Assume that two turns of the wire 1 have already been wound and the wire 1 is going to be wound on the core 2 to produce a third turn. The leading end portion 1A of the wire 1 is held between the rollers 23 and 23', and the intermediate portion 1B of the wire 1 is disposed in the slit 16 and forms a ring which includes the coil wound portion 4 of the core 2. The roller 21' is brought out of engagement with the roller 21 and moved away from the flat surface portion 14. The pad 40 is in the lower position and the pin 50 is in the upper position (as indicated by a line G in Fig. 29). The rollers 21', 22', 23', 24' and the pad 40 and pin 50 are disposed, when they are shown in phantom lines, in positions in which they are moved away or downwardly from the flat surface portion 14 shown in Fig. 5. Fig. 21 shows, on an enlarged scale, a portion of the core 2 shown in Fig. 20. In Fig. 21, the core 2 is positioned such that a lower end of the cover 12 coincides with a position of the wire 1. A portion of the wire 1 passed through the core window 3 of the core 2 disposed in this position is disposed in a space defined by the core 2 and annular wide guide 11 (or a position indicated by ) and does not overlap portions of the wire 1 (in positions and ) already wound on the core 2. At this time, the pad 40 is disposed such that its upper end is flush with the flat surface portion 14 of the base 10. When the coil winding section is in the condition shown in Fig. 20, the intermediate portion 1B or the wire 1 is in a phantom line position shown in Fig. 22 and urged by a corner 4B of the coil wound portion 4 (corresponding to a position of the wire 1 shown in Fig. 21) to bend, so that there is no risk that the wire 1 might be loosened in this position. Referring to Fig. 23, the leading end portion 1A of the wire 1 is fed by the rollers 23 and 23' from its position shown in Fig. 20 and guided in its movement by the annular wire guide 11 until it reaches the rollers 24 and 24'. Meanwhile the intermediate portion 1B of the wire 1 is fed by the rollers 22 and 22' and wound on the coil wound portion 4 of the core 2. At this time, the pad 40 is moved upwardly and forced against the inner surface of the cover 12. The intermediate portion 1B of the wire fed by the rollers 22 and 22' enters the slit 16 from the annular wire guide 11 to be introduced between the pad 40 and cover 12. Further rotation of the rollers 22 and 22' imparts a tension f to the intermediate portion 1B of the wire 1 to tighten same in a direction extending from the core 2 to the roller 22'. At this time, a reaction F is applied by the pad 40 to the intermediate portion 1B of the wire in the Z direction because the latter enters between the pad 40 and cover 12 as shown in Fig. 24. This causes the tension f imparted to the wire 1 by the rollers 22 and 22' as shown in Fig. 23 to be oriented in a direction extending along the cover 12, so that the wire moves along the cover 12 and is wound on the coil wound portion 4 of the core 2. Stated differently, the wire disposed in the position is wound on the coil wound portion 4 in the position , as shown in Fig. 24. Then, as shown in Fig. 25, the roller 22' is brought out of engagement with the roller 22 in the position shown in Fig. 23 and moved away from the flat surface portion 14. At this time, the intermediate portion 1B of the wire 1 is held between the pad 40 and cover 12, so that the portion 1C of the wire already wound on the core 2 and the intermediate portion 1B of the wire 1 held between the pad 40 and core 2 are kept from becoming loose. The roller 21' is brought into contact with the flat surface portion 14 and into engage­ ment with the roller 22 (as indicated by a line H in Fig. 29). The leading end portion 1A of the wire 1 is fed by the rollers 24 and 24' and guided in its movement by the annular wire guide 11 until it reaches the rollers 21 and 21'. Meanwhile the intermediate portion 1B of the wire 1 is fed by the rollers 23 and 23', so that it is pulled in a direction extending from the core 2 to the roller 23'. While the intermediate portion 1B is in this position, the roller 22' is brought into contact with the flat surface portion 14 and into engagement with the roller 22 (as indicated by a line I in Fig. 29). At this time, the core 2 is moved upwardly a distance corresponding to the diameter of the wire 1, as shown in Fig. 26. This causes a portion of the wire 1 extending from the position to the pad 40 to be wound on the coil wound portion 4 of the core 2 while it is kept in intimate contact with a portion of the wire 1 extending from the position to the position . At this time, the core 2 is positioned such that a lower end of the cover 12 coincides with a lower end of the portion of the wire 1. Then, as shown in Fig. 27, the sensor 8 senses the passage of the intermediate portion 1B of the wire 1 from its position shown in Fig. 25 and causes the roller 23' to be disengaged from the roller 23 and moved away from the flat surface portion 14, after lapse of a predetermined period of time. At this time, the intermediate portion 1B of the wire 1 is held between the pad 40 and cover 12, so that the portion 1C of the wire 1 already wound on the core 2 and the portion 1B of the wire 1 interposed between the pad 40 and cover 12 are kept from becoming loose. The leading end portion 1A of the wire 1 is fed by the rollers 21 and 21' and guided in its movement by the annular wire guide 11 until it reaches the wire inlet side of the core window 3 (as indicated by a line J in Fig. 29). Further rotation of the rollers 21 and 21' moves the leading end portion 1A of the wire 1 into the cutout 13 of the annular wire guide 11. The leading end portion 1A is able to pass through the core window 3 because it does not interfere with the portion 1C of the wire 1 which is already wound tightly on the coil wound portion 4 of the core 2. Referring to Fig. 28, the leading end portion 1A of the wire 1 that has passed through the core window 3 from its position shown in Fig. 27 is further fed by the rollers 21 and 21' and guided in its movement by the annular wire guide 11 until it reaches the rollers 22 and 22'. Meanwhile the intermediate portion 1B of the wire 1 is fed by the rollers 24 and 24' and abuts against the pin 50, so that it is brought to a position shown in a phantom line in Fig. 28. As the rollers 24 and 24' are further rotated, a reaction produced by the movement of the pin 50 in a direction indicated by a white arrow in Fig. 28 against the biasing force of the spring 56 shown in Fig. 19 tensions the intermedaite portion 1B of the wire 1 in a direction extending from the core 2 to the pin 50. As shown in Fig. 20, the roller 24' is brought out of engagement with the roller 24 in the position shown in Fig. 28 and moved away from the flat surface portion 14, and the pad 40 and pin 50 are moved downwardly. The roller 23' is brought into contact with the flat sur­ face portion 14 and into engagement with the roller 23 (as indicated by a line K in Fig. 29). The leading end portion 1A of the wire 1 is fed by the rollers 22 and 22' and guided in its movement by the annular wire guide 11 until it reaches the rollers 23 and 23'. Meanwhile the intermediate portion 1B of the wire 1 is fed by the rollers 21 and 21' and a ring of the wire 1 including the coil wound portion 4 of the core 2 and the roller 21' has its size gradually reduced into a smaller ring of the wire 1. At this time, the roller 21' is brought out of engagement with the roller 21 and moved away from the flat surface portion 14, and the pin 50 is moved upwardly. By performing the series of operations described hereinabove, one turn of the wire 1 is wound on the core 2. It is possible to produce a coil of the desired number of turns of the wire 1 by repeatedly performing the aforesaid operations a predetermined number of times. Fig. 22 shows the manner in which the wire 1 is wound on the coil wound portion 4 of the core 2. The wire 1 pulled in an A direction by the rollers 22 and 22' as shown in solid lines in Fig. 22 is tensioned in a B direction in Fig. 22 by the rollers 23 and 23' as shown in Fig. 25. Thus the wire 1 is subjected to plastic deformation and urged to bend by a corner 4A of the coil wound portion 4 of the core 2 as shown in phantom lines in the figure. The wire 1 is further tensioned, as shown in Fig. 28, by the rollers 24 and 24' and pin 50 in a C direction in Fig. 22. Thus the wire 1 is subjected to plastic deformation and urged to bend at the corner 4B of the coil wound portion 4 of the core 2 as shown in phantom lines in the figure. When the leading end portion 1A of the wire 1 is passed through the core window 3 and no tension is imparted to the intermediate portion 1B of the wire 1 any longer as shown in Fig. 20, the portion 1C of the wire 1 already wound on the core 2 (in solid lines) does not become loose because the wire 1 has been urged to bend as described hereinabove. Even if the wire 1 is pulled, as shown in Fig. 23, by the rollers 22 and 22' and tensioned in the A direction in Fig. 22, the coat on the wire 1 suffers little damage because it is only rubbed at corners 4C and 4D of the coil wound portion 4 of the core 2 as shown in solid lines in the figure. This is conducive to increased dielectric strength of the coil wound on the core 2. From the foregoing description, it will be appreciated that the second embodiment of the invention enables better alignment of the wire of the coil to be achieved by virtue of the arrangement whereby the range of movement of the wire through the core window is restricted by the annular wire guide and the wire is wound on the core while being tensioned in a predetermined direction to keep it from becoming loose. Also, the second embodiment enables the dielectric strength of the coil to be increased because the direction in which the wire is tensioned is varied to urge the wire to bend without becoming loose, to thereby reduce damage which the wire might otherwise suffer when it is wound on the core. In the second embodiment, the pad 40 and tensioning pin 50 are actuated to move the core 2 vertical­ ly each time the wire 1 is wound thereon. They may be actuated either singly or in combination. A third embodiment of the invention will now be described by referring to Figs. 30-33. This embodi­ ment is based on the first embodiment as is the case with the second embodiment, and intended to ensure that the operation of passing an extremely thin wire through a minuscule core window is performed with increased reliability. Fig. 30 is a perspective view of the apparatus for winding a wire on a core comprising the third embodiment additionally comprising a movable wire insertion guide 60 located in a cutout in the base 10 on the side of the core 2 in a cutout of the base 10. Fig. 31 is a view, on an enlarged scale, of the wire insertion guide 60. The wire insertion guide 60 is formed with a groove 61 having two opposite ends, one end being disposed in a wire outlet side of the path of the wire 1 between the rollers 21 and 21' and the other end being aligned with the core window 3. A shaft 62 of a pneumatic cylinder 63 mounted to the base 10 is force fitted in the wire insertion guide 60. As the pneumatic cylinder 63 is actuated, the wire insertion guide 60 is moved upwardly by the shaft 62 into engagement with the cover 12. Thus the cover 12 encloses the groove 61 to provide a completely enclosed wire guide. When the pneumatic cylinder 63 is deactuated, the wire insertion guide 60 is moved downwardly away from the cover 12 to define therebetween a clearance of substantially the same size as the slit 16. The operation of winding a coil on the core will now be described by referring to Figs. 32 and 33. Fig. 32 shows a condition of the apparatus corresponding to that shown in Fig. 17 after the coil winding has progressed in the same process as described by referring to the first embodiment. At this time, the wire insertion guide 60 is located in its upper position in which it is in contact with the cover 12 to provide a fully enclosed wire guide. Rotation of the rollers 21 and 21' feeds the leading end portion 1A of the wire 1 from its position in Fig. 32, and the wire insertion guide 60 and cover 12 guide the wire 1 so as to positively insert the leading end portion 1A in the core window 3. Fig. 33 shows the apparatus in a condition corresponding to that shown in Fig. 5 which shows the first embodiment. As shown, the wire insertion guide 60 is disposed in its lower position in which a clearance of substantially the same size as the slit 16 is defined between the wire insertion guide 60 and cover 12. Rotation of the rollers 22 and 22' reduces the size of a ring of wire formed by the intermediate portion 1B of the wire 1 as it moves toward the coil wound portion 4 of the core 2. The presence of the clearance of sub­ stantially the same size as the slit 16 between the wire insertion guide 60 and cover 12 facilitates the reduction in the size of the ring of wire because there is no obstacle to the movement of the intermediate portion 1B of the wire 1. In the third embodiment of the invention, when the leading end portion 1A of the wire 1 is passed through the core window 3 of the core 2 which is the only obstacle to the movement of the wire 1, the obstacle can be eliminated by the fully enclosed wire guide having no slit 16 provided by the wire insertion guide 60 cooperat­ ing with the cover 12, so that the leading end portion 1A can be positively passed through the core window 3. This is conducive to improved reliability of the coil winding operation performed by the method according to the invention. A fourth embodiment of the invention will now be described by referring to Figs. 34-39. This embodiment is based on the third embodiment and intended to ensure that the operation of passing an extremely thin wire of low rigidity through a minuscule core window is performed with increased reliability. Fig. 34 is a perspective view of the apparatus for winding a wire on a core comprising the fourth embodiment additionally comprising a plurality of nozzles 70 for feeding air currents from the slit 16 toward the annular wire guide 11, and a nozzle 65 for feeding air currents from the cover 12 above the wire insertion guide 60 toward the core window 3. Fig. 35 is a sectional view taken along the line XXXV-XXXV in Fig. 34. Formed in the base 10 in a position corresponding to a central portion of an area defined by the annular groove 11A is a cylindrical recess 71 formed with a sloping upper edge portion 72. A lid 74 for covering the upper open end of the cylindrical recess 71 is formed with a sloping lower edge portion 74 complementary with the sloping upper edge portion 72 of the base 10 and formed with a plurality of radial grooves 75. The lid 74 is screwed to the base 10 as indicated at 76. The sloping upper edge portion 72 of the base 10 cooperates with the grooves 75 to define the nozzles 70 which are connected through the cylindrical recess 71 and a duct 77 via joint 78 to a source of compressed air, not shown. Fig. 36 is a view, on an enlarged scale, of the portion D shown in Fig. 34, in which the nozzle 65 is mounted to the cover 12 above the wire insertion guide 60 shown in Fig. 31 for feeding air currents toward the core window 3. The nozzle 65 is connected via a joint 67 to a source of compressed air, not shown. The operation of winding a coil on the core will now be described by referring to Figs. 37-39. Fig. 37 shows the apparatus in a condition corresponding to that shown in Fig. 32 after coil winding has progressed in the same manner as described by referring to the third embodiment. At this time, the wire insertion guide 60 is in its upper position in which it is in contact with the cover 12 to provide a fully enclosed wire guide. Rotation of the rollers 21 and 21' feeds the leading end portion 1A of the wire 1 from its position shown in Fig. 37, and the leading end portion 1A is positively guided by the wire guide provided by the wire insertion guide 60 and cover 12 and inserted in the core window 3. At this time, an air current 65A supplied through the nozzle 65 in turbulent flow exerts a non-­ steady force on the leading end portion 1A in the wire insertion guide 60 as shown in Fig. 38, so that the lead­ ing end portion 1A moves while vibrating at high speed and with a small amplitude as shown in phantom lines in the figure. This keeps the leading end portion 1A from catching against the portion 1C of the wire 1 already wound on the core, even if the leading end portion 1A strikes the wound portion 1C of the wire 1, thereby allowing the leading end portion 1A to positively pass through the core window 3. Referring to Fig. 39, the leading end portion 1A of the wire 1 is fed by the rollers 21 and 21' after passing through the core window 3 and guided in its movement by the annular wire guide 11, until it reaches the rollers 23 and 23' after passing through the rollers 22 and 22'. Generally, when the wire 1 is low in rigidity, the leading end portion 1A has a tendency such that it is bent by the impact of its collision with the rollers 21, 21', 22, 22', 23, 23' and 24, 24' or by the reaction of the annular wire guide 11, with the result that it might inadvertently enter the slit 16. In the fourth embodi­ ment of the invention, the leading end portion 1A is fed while being forced by air currents 70A from the nozzles 70 into the annular wire guide 11. Thus the leading end portion 1A can be positively fed to the core window 3 without deviating from the annular wire guide 11 and entering the slit 16. Meanwhile the intermediate portion 1B of the wire 1 which is fed by the rollers 21 and 21' is moved toward the slit 16 by reducing the size of a ring formed thereby against the air currents 70A supplied through the nozzles 70. In the fourth embodiment of the invention, the wire of low rigidity can be positively inserted in the core window because it is caused by the air currents in turbulent flow to vibrate at high speed and with a small amplitude when the leading end portion is inserted in the core window. Thus the leading end portion can be positively inserted in the core window regardless of the size of the core window, the rigidity of the wire and the number of turns of the coil desired to be produced. Additionally, the use of the air currents enables the leading end portion to be positively guided, even if the wire is low in rigidity. The constituent elements of the apparatus comprising the first to fourth embodiments of the invention may be used either singly or in combination as desired. From the foregoing description, it will be appreciated that the invention can achieve the following advantages: it is possible to positively wind a coil in a plurality of number of turns because the wire is fed by a plurality of pairs of rollers and guided in its movement by an annular wire guide; coil winding can be performed at high speed because the wire can be continuously passed through the core window and wound on the core in a plurality of number of turns; and it is possible to obtain an overall compact size in a coil winding apparatus and to reduce its cost because the mechanism is simple in construction. Thus the invention provides an automatic coil winding apparatus which is high in operation speed, compact in size and reliable in performance. Additionally, the coil winding operation can be performed at high speed because feeding and tensioning the wire can be continuously effected, and the reliability in performance can be increased because the wire can be positively guided by means of the annular wire guide and movable wire insertion guide.

Claims: 1. A method of winding a coil on a toroidal core comprising the steps of: feeding a leading end portion of the wire by feed roller means along annular wire guide means; inserting the leading end portion of the wire from a wire inlet side into a core window arranged in a position in which it faces the annular wire guide means; pulling the leading end portion from a wire outlet side of the core window by means of the feed roller means while bringing a roller of the feed roller means out of engagement with an associated roller; and winding the leading end portion of the wire on the toroidal core by reducing the size of a ring formed by an intermediate portion of the wire by means of the feed roller means while passing the ring through a slit. 2. A method of winding a coil on a toroidal core as claimed in claim 1, wherein coil winding can be performed in such a manner that convolutions of the wire wound on the toroidal core are correctly positioned by means of a pad supported for vertical movement on the wire outlet side of the core window and a pin supported for vertical and pivotal movements in a position sub­ stantially diametrically opposite the pad. 3. A method of winding a coil on a toroidal core as claimed in claim 1, wherein a wire insertion portion of said annular wire guide means is rendered movable in a vertical direction, said wire insertion portion being moved into contact with a cover to provide a sealed wire guide when the leading end portion of the wire is passed through the core window. 4. A method of winding a coil on a toroidal core as claimed in claim 1, wherein air currents are fed from the slit toward the annular wire guide means while the wire is being wound on the toroidal core. 5. A method of winding a coil on a toroidal core as claimed in claim 1, wherein the wire is wound on the core while air currents are being fed from the wire inlet side of the core window toward the core window. 6. An apparatus for winding a coil on a toroidal core comprising: annular wire guide means (11, 11A) formed with a cutout (13); feed roller means including a plurality of pairs of feed rollers (21, 21', 22, 22', 23, 23', 24, 24'), the rollers of each pair engaging each other inside the annular wire guide means (11, 11A) and having axes of rotation located perpendi­ cular to a plane in which the annular wire guide means is located; at least one core holding unit (6A, 6B) for holding the toroidal core (2) in a position in which a wire wound por­ tion of the toroidal core (2) is disposed in said cutout (13) of the annular wire guide means (11, 11A); moving means (34 - 39) for bringing the rollers (21', 22', 23', 24') of the plurality of pairs of rollers which are located inside the annular wire guide means (11, 11A) out of engagement with the respective associated rollers (21, 22, 23, 24) and moving same away from the plane in which the annular wire guide means is located; and a drive (32) for driving said feed rollers for rotation. 7. An apparatus for winding a coil on a toroidal core as claimed in claim 6, further comprising a pad (40) supported for vertical movement in a position disposed on the wire outlet side of the core (2) disposed inside the annular wire guide (11, 11A). (Fig. 17, 18). 8. An apparatus for winding a coil on a toroidal core as claimed in claim 6 or 7, further comprising a pin (50) supported for vertical and pivotal movements in a position substantially diametrically opposite said toroidal core (2). (Fig. 17, 19). 9. An apparatus for winding a coil on a toroidal core as claimed in claim 8, further comprising sensor means (8) located on an imaginary straight line connecting the toroidal core to one of the plurality of pairs of rollers of the feed roller means for monitoring the passage of the wire. 10. An apparatus for winding a coil on a toroidal core as claimed in claim 6, further comprising wire insertion guide means (60) supported for vertical movement in a po­ sition disposed in a cutout formed in a base and located on the wire insertion side of the core. (Fig. 30, 31) 11. An apparatus for winding a coil on a toroidal core as claimed in claim 6, further comprising first nozzle means (70) for feeding air currents (70A) from a slit toward the annular wire guide means. 12. An apparatus for winding a coil on a toroidal core as claimed in claim 6, further comprising second nozzle means (65) for feeding air currents (65A) toward the toroidal core from the wire insertion side thereof. 13. An apparatus for winding a coil on a toroidal core comprising: annular wire guide means; a slit disposed inside said annular wire guide means; feed roller means including a plurality of pairs of rollers for feeding the wire along said wire guide means; means for bringing the rollers of the plurality of pairs of rollers which are located inside the annular wire guide means out of engagement with the respective associated rollers, and at least one core holding unit for holding the toroidal core in a position in which a core window is disposed in a portion of the annular wire guide means. 14. An apparatus for winding a coil on a toroidal core as claimed in claim 13, further comprising means for holding the wire inside the annular wire guide means, and a pin for controlling the direction or the intensity of tension imparted to the wire, wherein the core is moved vertically a distance corresponding to the diameter of the wire each time one turn of the wire is wound. 15. An apparatus for winding a coil on a toroidal core as claimed in claim 13, further comprising movable wire guide means located on the wire insertion side of the core window. 16. An apparatus for winding a coil on a toroidal core as claimed in claim 13, further comprising nozzle means for feeding air currents from the slit toward the annular wire guide means, and another nozzle means for feeding air currents from the wire insertion side toward the core window.

Inventors: FUKUMOTO, YOUSHUKE, HAMADA, TOYOHIDE, HARA, SHIGEO, OHASHI, TOSHIJIRO, SATO, HIROSHI, SUZUKI, TAKAMICHI, UMAKOSHI, YUKIMORI, WADA, YUUJI
Applicants: HITACHI, LTD.
Application year: 1986
Main classification: H01F41
IPC codes: H01F41, G11B5