Coil winding machine

Abstract: A reel for supplying film, a main nip for gripping the front end of this film and moving the film, a tension nip for gripping the film withdrawn by the main nip, and a cutter for cutting the film on the reel side of the tension nip, are provided. Before the film is wound on a coil, the front end of the film is gripped by the main nip and withdrawn from the reel, then the cutter cuts the film while the tension nip grips the film at a predetermined position. The cutting of the film is therefore performed concurrently with the winding of coil. The cut length of film may also be set to, any desired length by varying the distance through which the main nip gripping the film moves.

Description: FIELD OF THE INVENTION This invention relates to a machine for winding a coil such as a flyback transformer or the like, and more specifically, to a mechanism that winds an insulating film on a coil. BACKGROUND OF THE INVENTION Some coils used in flyback transformers or the like comprise layers of coil windings and insulating film alternately superposed on each other. In other words, an insulating film is wound over a coil wound on a coil bobbin, coil is wound over the film, and insulating film is then again wound on the coil. A method of winding a film on such a coil is disclosed for example in Tokkai Hei 5-101961 published by the Japanese Patent Office in 1993. In this method, an insulating film is gripped by two grips known as a front nip and a rear nip. One end of the insulating film wound on a reel is first gripped by the front nip, the film is withdrawn from the reel, and the front end of the film is then heated so as to weld it to the coil. Next, the front nip releases the film, returns to near a cutting position, and the film is gripped near the cutting position by the rear nip and front nip. After the film is cut by a cutter between the rear nip and front nip, a bobbin is rotated so as to wind the film onto the bobbin. In this process, the rear end of the film is gripped by the rear nip and a predetermined tension is applied to the film so that it is wound on the bobbin without any slack. In this winding process, as the film is cut after its front end has been attached to the bobbin, the winding length of the film is determined by the distance between the cutter and the bobbin. If the position of the cutter is fixed and it is desired to change the winding length, the position of the bobbin must be changed. From the viewpoint of efficiency, the film is preferably cut during the coil winding operation, and the film then wound alone after the coil winding operation. In the aforesaid winding method, however, the film is cut after the front end of the film has been attached to the bobbin, so it cannot be cut first. SUMMARY OF THE INVENTION It is therefore an object of this invention to modify the film length as desired without changing the coil bobbin position. It is a further object of this invention to perform film cutting in parallel with coil winding. In order to achieve the above object, this invention provides a coil winding machine comprising a coil winding mechanism for winding a coil on a rotating coil bobbin, and a film winding mechanism for winding an insulating film on the coil. The film winding mechanism comprises a reel for supplying film, a main nip for gripping the front end of the film, a mechanism for moving the main nip in a predetermined direction, a tension nip for gripping the film withdrawn by the main nip at a predetermined position, a cutter for cutting the film on the reel side of the tension nip, a mechanism for moving the tension nip that has gripped the film in the predetermined direction together with the main nip, and a mechanism for returning the tension nip that has released the film to the predetermined position. The tension nip moving mechanism preferably comprises a mechanism for moving the main nip and a guide for guiding the tension nip such that it is free to be displaced in the predetermined direction, and the returning mechanism comprises a mechanism for pushing the tension nip toward the predetermined position. The pushing mechanism preferably comprises an air cylinder and a mechanism for supplying air to the air cylinder. Alternatively, the pushing mechanism comprises a belt passing over two pulleys arranged in a vertical direction and a counterweight joined to the belt, and the tension nip is linked to this belt. The guide is preferably provided with a mechanism for adjusting guide angle. It is also preferable that the coil winding machine further comprises a mechanism for moving the coil bobbin. The details as well as other features and advantages of this invention are set forth in the remainder of the specification and are shown in the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a coil winding machine according to this invention. Fig. 2 is a perspective view of a cutter according to this invention. Fig. 3 is a side view of a film winding mechanism according to this invention. Fig. 4 is a side view of the film winding mechanism seen from a direction perpendicular to that of Fig. 3. Fig. 5 is similar to Fig. 4, but showing another embodiment of the invention. DESCRIPTION OF THE PREFERRED EMBODIMENTS An automatic coil winding machine shown in Fig. 1 of the drawings winds a coil and a film 7 on a coil bobbin 1. This automatic coil winding machine comprises a spindle 3 supported by a moving mechanism 4, a nozzle 5 for feeding out wire, and a conveyor 6 for transporting the coil bobbin 1, these components being mounted on a base 12. The automatic coil winder fits the coil bobbin 1, which has been transported on the base 12 by the conveyor 6, onto the spindle 3 when the spindle 3 is moved by the moving mechanism 4. Subsequently, the end of the wire supplied by the nozzle 5 is attached to a predetermined area of the coil bobbin 1, the spindle 3 is rotated and the wire is thereby wound on the coil bobbin 1. The insulating film 7 is wound on the coil bobbin 1 at each coil layer, and for this purpose the coil winding machine is provided also with a film winding mechanism. This film winding mechanism comprises a reel 8 for supplying the film 7, a film punch 9 that forms a notch in the film 7 paid out from the reel 8, and an embosser 10 that impresses a wavy pattern on the film 7, all these components being mounted on the base 12. A main nip 13 and tension nip 14 that grip the film 7, and a cutter 15, are installed beneath the embosser 10. The main nip 13 comprises a pair of members that open and close when driven by an air cylinder 20. The main nip 13 is supported by an arm 17 that screws on to a vertically oriented spindle 16 mounted on the base 12, and is moved up or down by the operation of a motor 18 connected to the spindle 16. The main nip 13 moves effectively parallel to the spindle 3 within predetermined limits according to the driving power of an air cylinder 19 situated between the nip 13 and the arm 17. The tension nip 14, which is similar to the main nip 13 and projects downwards at an angle from the base 12, is attached to a bracket 32 which is guided free to move up and down in a guide 22, as shown in Fig. 3 and Fig. 4. This bracket 32 is connected to an air cylinder 21. The air cylinder 21 is compressed by internal compressed air, and when it is in its most compressed position, the tension nip 14 is held in its starting position directly beneath the cutter 15 as shown by the solid line in Fig. 3. Two compressed air supplies 23, i.e. low pressure and high pressure, are connected to the air cylinder 21. The tension nip 14 is provided with an air cylinder 24 that opens or closes it, and it grips the film 7 on the side opposite to the main nip 13. The main nip 13 and tension nip 14 are of such dimensions that their front ends cannot interfere with each other, thereby permitting the main nip to move upwards from the tension nip 14. The guide 22 is formed in a one-piece construction with a guide platform 41 supported free to rotate on the base 12 via a pivot 40. An adjusting screw 42 screws into the upper end of the guide platform 41 in order to adjust the inclination of the guide 22. This front end passes through the guide platform 41 so as to come in contact with the base 12. By rotating this adjusting screw 42, the guide platform 41 is made to tilt forwards or backwards through a small angle from the upright position about the pivot 40. The cutter 15 is situated directly beneath the embosser 10, and cuts the film 7 by gripping it from both sides due to the driving force of two air cylinders 25. The cutter 15 comprises a blade 15A that cuts the film 7, and a press 15B pushed by a spring 34 so as to press the film 7 above the blade 15A as shown in Fig. 2. These components are installed effectively parallel to the opening and closing members of the tension nip 14, as shown in Fig. 4, so as to cut the film 7 obliquely from a horizontal direction. Further, when the cutter 15 is open, it has an aperture that is sufficient to allow the main nip 13 to pass through it. The film winding mechanism comprises a welding head 26 for welding the film 7 to the coil bobbin 1 and a film press 27 that presses the film 7 on the coil bobbin 1, these components being installed in the lower part of the base 12. By means of this construction, the welding head 26 comes into contact with part of the film 7 and heats it while the front or rear end of the film 7 is being pressed on the outer circumference of the coil bobbin 1 by the press 27, and the film 7 is thereby welded to the coil bobbin 1. The welding head 26 and film press 27 are supported on the base 12 via drive mechanisms required to perform these actions. In this coil winding machine, the machining of the film 7 by the film punch 9 and embosser 10, and the cutting of the film 7 by the cutter 15, are performed concurrently together with the winding of the coil. In order to cut the film 7, the main nip 13 is first raised by a motor 18 so that it lies directly underneath the embosser 10, and the front end of the film 7 is gripped. As it moves upwards, the cutter 15 is held open, and the main nip 13 reaches the grip position above the cutter 15. Due to the action of the air cylinder 20, the film 7 is then gripped, and the main nip 13 is lowered to a predetermined position by again operating the motor 18. This causes the film 7 to be paid out from the reel 8. When the main nip 13 has reached the predetermined position, the tension nip 14 grips the film 7 directly beneath the cutter 15 due to the action of the air cylinder 24, and the cutter 15 cuts the film 7 due to the action of the air cylinders 25. The machining of the film 7 by the film punch 9 and embosser 10 is performed before the film 7 is withdrawn by the main nip 13, however the film punch 9 and embosser 10 may be operated in the course of film withdrawal, by temporarily stopping the main nip 13. In this way, any desired part of the film 7 can be machined. Likewise, the cut length of the film 7 may be set as desired by changing the stopping position of the main nip 13. The front and rear ends of the cut film 7 are gripped respectively by the main nip 13 and tension nip 14, and the whole of the film 7 is moved when the main nip 13 is moved by the motor 18. Low pressure air is then supplied to the air cylinder 21 from the compressed air supply mechanism 23, and the tension nip 14 is displaced against the compressive force of the air cylinder 21 as a predetermined low tension is applied to the film 7. The pressure supplied by the compressed air supply mechanism 23 to the air cylinder 21 is maintained constant, hence the tension in the film 7 is also maintained constant regardless of the displacement position. The main nip 13 stops moving downwards when the front end of the film 7 reaches one side of the coil bobbin 1. All the aforesaid operations are performed concurrently with the winding of coil on the coil bobbin 1. After one layer of coil has been wound, the coil bobbin 1 on the spindle 3 is moved sideways due to the action of the drive mechanism 4, and is brought into contact from one side with the front end of the film 7 supported by the main nip 13. The film press 27 then presses the film 7 on the coil bobbin 1, the welding head 26 comes into contact with the film 7, and the contact part is heated so that the film 7 is welded to the outer circumference of the coil bobbin 1. Next, the main nip 13 is released, the spindle 3 is rotated, and the film 7 whereof the front end is attached to the coil bobbin 1 is wound on the coil bobbin 1. The air cylinder 21 of the tension nip 14 that grips the rear end of the film 7 is still maintained under low pressure. This is in order to prevent an excessive tension from acting on the film 7 immediately after welding. The air cylinder 21 is changed over to high pressure so as to increase the tension in the film 7 once winding has proceeded to some extent, and the film 7 can therefore be wound on the coil bobbin 1 without any slack. The tension nip 14 descends in the guide 22 as it grips the rear end of the film 7, hence the film 7 can be accurately wound on the same position of the coil bobbin 1 up to its rear end without any offset. The inclination of the guide 22 can be adjusted by means of the adjusting screw 42. When the adjusting screw 42 is rotated, the position at which the tension nip 14 grips the film 7 is changed. The tension nip 14 moves guided by the guide 22, however as the base end of the guide 22 is situated near the pivot 40, its position is effectively constant regardless of the rotation of the adjusting screw 42. Rotating the adjusting screw 42, therefore, slightly changes the angle between the film 7 and the rotation axis of the coil bobbin 3. Hence, if the film 7 tends to lean to one side of the coil bobbin 1 as winding proceeds, the sideways shift of the film 7 wound on the coil bobbin 1 can easily be corrected by rotating the adjusting screw 42. After the winding of the film 7 is complete, the tension nip 14 is released, the rear end of the film 7 is pressed against the coil bobbin 1 by again driving the film press 27, and the rear end of the film 7 is welded to the outer circumference of the coil bobbin 1 by the welding head 26. At the same time, the tension nip 14 that has released the film 7 is pushed upwards by the air cylinder 21 under high pressure, and is therefore rapidly raised to its starting position directly beneath the cutter 15. This completes the winding of the film 7. The coil bobbin 1 then again moves to the coil winding position, and the next layer of coil is wound on the film 7. Cutting and machining of the film 7 are therefore performed concurrently with the coil winding process, and as only winding is performed during the film winding process, less time is required for winding the film 7 and the coil can be manufactured with high efficiency. The coil diameter increases as coil winding proceeds, however the welding position of the film 7 is maintained constant by varying the position of the spindle 3 by means of the displacement mechanism 4. The welding position of the film 7 may also be maintained constant when coil bobbins of different outer diameter are used. Fig. 5 shows another embodiment of this invention regarding the means used to push the tension nip 14. According to this embodiment, a belt 30 and counterweight 33 are used instead of the air cylinder 21. The belt 30 passes round upper and lower pulleys 31, the tension nip 14 being attached to the belt 30 via the bracket 32 guided by the guide rail 22. The counterweight 33 which is slightly heavier than the combined weight of the tension nip 14 and bracket 32 is attached to the belt 30 on the opposite side of the tension nip 14. The position at which the counterweight 33 is attached is chosen so that the lowermost position to which the counterweight 33 descends is the film grip position of the tension nip 14. According to this embodiment, when the cut film 7 descends while being gripped by the main nip 13, the counterweight 33 resists the displacement of the tension nip 14 which follows the main nip 13, and a predetermined tension is thereby applied to the film 7. Further, the tension nip 14 that has released the film 7 is automatically pulled up to the starting position directly beneath the cutter 15 due to the balancing effect of the counterweight 33. According to this embodiment, the film winding mechanism can be constructed more simply and economically than the mechanism according to the first embodiment where the tension nip 14 is pushed by the air cylinder 21 and the compressed air supply mechanism 23. In any of the aforesaid embodiments, the tension nip 14 does not have its own moving means. When the tension nip 14 grips the film 7, it follows the main nip 13 guided by the guide 22, and when it has released the film 7, it is returned to a predetermined position by a pushing means. The tension nip 14 may however also be provided with a displacing mechanism of the same type as that used for the main nip 13, and these two displacing mechanisms made to operate in synchronism. The embodiments of this invention in which an exclusive property or privilege is claimed are defined as follows:

Claims: A coil winding machine comprising a coil winding mechanism for winding a coil on a rotating coil bobbin (1), and a film winding mechanism for winding an insulating film (7) on said coil, characterized in that said film winding mechanism comprises: a reel (8) for supplying film (7), a main nip (13) for gripping the front end of said film (7), means (18) for moving said main nip (13) in a predetermined direction, a tension nip (14) for gripping said film (7) withdrawn by said main nip (13) at a predetermined position, a cutter (15) for cutting said film (7) on the reel side of said tension nip (14), means for moving said tension nip (14) that has gripped said film (7) in said predetermined direction together with said main nip (13), and means for returning said tension nip (14) that has released said film (7) to said predetermined position. A coil winding machine as defined in claim 1, wherein said tension nip moving means comprises means (18) for moving said main nip (13) and a guide (22) for guiding said tension nip (14) such that it is free to be displaced in said predetermined direction, and said returning means comprises means for pushing said tension nip (14) toward said predetermined position. A coil winding machine as defined in claim 2, wherein said pushing means comprises an air cylinder (21) and a mechanism (23) for supplying air to said air cylinder (21). A coil winding machine as defined in claim 2, wherein said pushing means comprises a belt (30) passing over two pulleys (31) arranged in a vertical direction and a counterweight (33) joined to said belt (30), said tension nip (14) being linked to this belt (30). A coil winding machine as defined in claim 2, wherein said guide (22) is provided with a mechanism (42) for adjusting guide angle. A coil winding machine as defined in claim 1, wherein said machine further comprises means (4) for moving said coil bobbin (1).

Inventors: HONDA HIDEMITSU, HONDA, HIDEMITSU, HONDA, HIDEMITSU, C/O FUKUSHIMA FACTORY OF
Applicants: NITTOKU ENG, NITTOKU ENGINEERING KABUSHIKI KAISHA
Application year: 1995
Main classification: H01F41
IPC codes: H01F41