APPARATUS FOR POSITIONING MAGNETIC HEAD

Abstract: A magnetic head positioning apparatus includes a chassis, a driving device provided on the chassis, a guide member provided on the chassis, a carrier movably provid­ ed on the guide member, a first metallic head, support mounted on the carrier and adapted to support a first mag­ netic head, and a second metallic head support mounted on the carrier and adapted to support a second magnetic head which is disposed to oppose the first magnetic head. A coupling member is formed on the first head support and di­ rectly connected to the driving device. By moving the cou­ pling member by the operation of the driving device, the carrier is moved along the guide member through the first head support. Thus, it is possible for the magnetic head po­ sitioning apparatus to possess excellent resistance to envi­ ronmental changes and to effect highly accurate positioning of the magnetic heads.

Description: BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The present invention relates to an apparatus for positioning magnetic heads which are used to effect recording and reproducing in relation to a flexible double-sided magnetic disk. DESCRIPTION OF THE PRIOT ART A typical conventional apparatus of the type described above has been arranged, as mentioned, for example, in the specification of Japanese Patent Laid-Open No. JP-A-55.077.028, such that one of the magnetic heads is directly secured to a carrier of a synthetic resin which is slidable on a guide shaft, and the other magnetic head is secured to an arm of a synthetic resin which is mounted on the carrier. This arrangement, however, suffers from the disadvantage that changes occurring in the synthetic resin portions with fluctuations in temperature and relative humidity or with time unfavorably lower the degree of positioning accuracy of the magnetic heads. Such changes make it particularly easy for displacement to take place between two magnetic heads which oppose each other across a double-sided magnetic disk. Further, to respectively mount the magnetic heads on the carrier and the arm by employing thin metallic gimbals, it is necessary to respectively secure the gimbals to the carrier and the arm by means of an adhesive since the carrier and the arm are both made of a synthetic resin. However, this bonding between the gimbals and the carrier and the arm by means of an adhesive is easily affected by changes occurring in the adhesive with fluctuations in temperature and relative humidity or with time and is thereby made disadvantageously unstable, so that it is difficult to effect highly accurate positioning of the magnetic heads. EP-A-0 012 844 is concerned with apparatus for positioning magnetic heads with respect to a thin flexible disc for data transfer. The apparatus comprises a pair of parallel, rigid, metal arms which are swingable apart by being mounted each at one end on a common leaf spring having two legs, one for each of said arms. At its free end each arm carries a transducer, the transducers being in opposed facing alignment. The leaf spring is mounted on a carriage slidable along guide rods extending parallel with the plane of the disc so that the transducers can move radially across and in contact with the oposite surfaces of the disc. No means for displacing this apparatus radially of the disc is disclosed. GB-A-2 081 959 is concerned with an apparatus for use with a flexible magnetic disc housed within a cassette. The cassette has in each of its two major faces a radially extending aperture, the two apertures being in opposed alignment. The disc is mountable on a recording and/or reproducing device having a drive shaft for driving the disc via a central hole in the cassette. Said device also includes a magnetic head that extends through one of said radially extending apertures to engage the disc in the cassette. The magnetic head is mounted on a carrier member slidable along a rod, the carrier member being driven back and forth along said rod by means of a screw drive rotated by a stepping motor, the arrangement being such that the magnetic head can be moved back and forth along the length of the radially extending aperture through which it engages the disc in the cassette. Projecting through the other radially extending aperture of the cassette is a disc pressing member aligned with the magnetic head. The disc pressing member is carried by an arm mounted on said carrier member, said arm being spring biassed to press the pressing member against the disc. SUMMARY OF THE INVENTION It is a primary object of the present invention to provide a magnetic head positioning apparatus which suffers greatly reduced changes in its essential portions with fluctuations in temperature and relative humidity or with time and consequently allows the magnetic heads to be positioned with high acccuracy. To this end, the present invention provides a magnetic head positioning apparatus for a magnetic disc as defined in the accompanying Claim 1. BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings in combination show one embodiment of the present invention, in which: Fig. 1 is a perspective view of an essential portion of the embodiment in an assembled state; Fig. 2 is a sectional view of an essential portion of the embodiment before insertion of a magnetic disk therein; Fig. 3 is a sectional view of the essential portion shown in Fig. 2 after insertion of the magnetic disk therein; Fig. 4 is a plan view of an essential portion of the embodiment in an assembled state; Fig. 5 is a side elevational view of the essential portion shown in Fig. 4 in an assembled state; and Fig. 6 is an exploded perspective view of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT One embodiment of the present invention will be described hereinunder with reference to the accompanying drawings. In the drawings, a chassis 1 of a magnetic recording and reproducing apparatus is made from a steel sheet. A support plate 2 which is employed to mount the magnetic recording and reproducing apparatus onto another device, such as a personal computer, is secured to the chassis 1 by screws or other fixing means. A front panel 3 is secured to the front side of the chassis 1 by screws or other fixing means. The front panel 3 is provided with an opening 3a for loading and unloading a cartridge 5 which houses a flexible double-sided magnetic disk 4. A holder 6 made from a steel sheet is vertically movably supported by four support members 7 of a synthetic resin which are projected from the surface of the chassis 1 at its end portions. The support members 7 are respectively formed with guide grooves 7a. On the other hand, the holder 6 is provided at its side edges with rollers 8 which are engageable with the corresponding guide grooves 7a. An eject lever 9 made from a steel sheet is installed such as to be movable on the chassis 1. Each of coiled springs 10 has one of its ends retained by one of mounting pieces 1a which is projected from the surface of the chassis 1 and the other end retained by one of mounting pieces 9a which is formed on the eject lever 9. A resilient retainer 11 has an L-shaped lever 11a, a coiled spring 11b and a mounting pin 11c which is used to mount the coiled spring 11b and the lever 11a to the chassis 1. The arrangement is such that, when the eject lever 9 is moved rearwardly and a retainer opening 9b provided in the eject lever 9 is engaged with a retaining bent portion 11d formed on the lever 11a, this engagement state is maintained by the resilient force of the coiled spring 11b. When the lever 11a is pivoted against the resilient force of the coiled spring 11b, the above-described engagement is cancelled, and the eject lever 9 is moved forwardly by the action of the coiled springs 10 such as to be restored to its previous state. As the cartridge 5 is inserted into the holder 6 from the opening 3a, a retainer pin 13 provided on a lever 12 which is pivotally supported on the holder 6 is planarly moved against the resilient force of a tension spring 14 in such a manner that the retainer pin 13 opens a shutter (not shown) of the cartridge 5. As the cartridge 5 is further forced into the holder 6, the cartridge 5 abuts against the lever 11a, causing it to pivot about the retainer pin 13. In consequence, the engagement between the eject lever 9 and the lever 11a is cancelled, and the eject lever 9 is moved forwardly by the action of the coiled springs 10. The eject lever 9 has guide grooves 9c formed in bent portions at both ends. The guide grooves 9c allow the corresponding rollers 8 provided on the holder 6 to lower along the respective guide grooves 7a when the eject lever 9 is moved forwardly. When the rollers 8 lower along the respective guide grooves 7a, the holder 6 lowers correspondingly, whereby the hub 4a of the magnetic disk 4 is fitted on a hub holder 16 of a magnetic disk driving device 15 constituted by a direct drive motor which is secured to the chassis 1. A first magnetic head 17 which effects recording and reproducing in relation to the magnetic disk 4 is mounted on a first head support 18 made from a metal sheet, e.g., a stainless steel sheet, with a thickness of 0.3 to 0.5 mm through a gimbals 19 made from a metal sheet, e.g., a stainless steel sheet, with a thickness of 0.05 to 0.08 mm. A second magnetic head 20 effects recording and reproducing in relation to the side of the magnetic disk 4 which is opposite to the side thereof on which the first magnetic head 17 effects recording and reproducing operations. The second magnetic head 20 is mounted on a second head support 21 made from a metal sheet, e.g., a stainless steel sheet, with a thickness of 0.3 to 0.5 mm through a gimbals 22 made from a metal sheet, e.g., a stainless steel sheet, with a thickness of 0.05 to 0.08 mm. The gimbals 19 and 22 are respectively welded to the first and second head supports 18 and 21. The first head support 18 is integrally formed with a coupling member 23 which projects to a large degree from the side of the support 18. In accordance with this embodiment, the first head support 18 and the coupling member 23 are formed by blanking a single stainless steel sheet, but the formation thereof is not necessarily limitative thereto. It is possible to form the first head support 18 and the coupling member 23 as separate members and to weld them together when the apparatus is assembled. A guide member 26 made from a metal rod is mounted on the chassis 1 by employing mounting pieces 1b which project from the surface of the chassis 1 and mounting members 24 each made of a leaf spring material as well as mounting screws 25. A carrier 27 made of a synthetic resin is movably mounted on the guide member 26. The first and second head supports 18 and 21 are mounted on the carrier 27 in such a manner as to clamp the carrier 27. The respective mounting positions of the head supports 18 and 21 are set such that the first and second magnetic heads 17 and 20 oppose each other. The second head support 21 is composed of a member 21a which supports the second magnetic head 20, and a member 21b constituted by a metal member which is smaller in thickness than the member 21a, so that the member 21a is held such as to be upwardly swingable. The members 21a and 21b are integrated with each other by caulking. The second head support 21 has bent pieces 21c formed at both its side edges. The bent pieces 21c project outwardly from the surface 21d of the second head support 21 which is opposite to the surface thereof for mounting the second magnetic head 20 and extend in the longitudinal direction of the second head support 21. The chassis 1 is provided thereon with a driving device 28 for positioning the first and second magnetic heads 17 and 20. The driving device 28 includes a motor 28a constituted by, e.g., a stepping motor, a screw 28b rotated both forwardly and backwardly by the operation of the motor 28a, and a mounting plate 28c employed to screw the motor 28a to the chassis 1. The screw 28b and the coupling member 23 are directly connected together by a screw nut 28d in such a manner that the coupling member 23 moves on the screw 28b as it rotates. The first head support 18 has bent pieces 18a formed at both its side edges. The bent pieces 18a project outwardly from the surface of the first head support 18 which is opposite to the surface 18b for mounting the first magnetic head 17 and extend in the longitudinal direction of the first head support 18. The first head support 18, the carrier 27 and the second head support 21 are integrated together by fastening means constituted by screws 29. The carrier 27 is provided with through-holes 27a for receiving the respective screws 29. The through-holes 27a are respectively provided therein with metallic distant pieces 30 by insert molding or press fitting. A spring device 31 is adapted to press the second head support 21 in such a direction that the second magnetic head 20 is pressed against the first magnetic head 17. It is necessary for the spring device 31 to include, at least, a coiled spring 31a and a mounting member 31b made from a steel sheet which is employed to mount the coiled spring 31a. The mounting member 31b is secured on the carrier fitting member 21b of the second head support 21 by the use of the screws 29. The mounting member 31b is integrally formed with a member 31c for mounting an interlock adjusting member 32b of a position sensor 32. The position sensor 32 defines and senses the initial position of the carrier 27. The second head support 21 is provided with an arm 33 employed to upwardly swing the second head support 21, and a terminal plate 35 for effecting electrical connection of a flexible cord 34 which is connected to the second magnetic head 20. The arm 33 and the terminal plate 35 are integrally molded from a synthetic resin having excellent electrical insulating properties. The respective mounting positions of the arm 33 and the coiled spring 31a of the spring device 31 are located in a substantially straight line extending in a direction orthogonal to the longitudinal direction of the second head support 21. A flexible cord 36 which is connected to the first magnetic head 17 is electrically connected with a head cord 37, while the flexible cord 34 connected to the second magnetic head 20 is electrically connected with a head cord 38. A tension spring 39 has one of its ends retained by a notch 23a formed in the coupling member 23 and the other end retained by a mounting piece 1c which projects from the surface of the chassis 1. Thus, both the coupling member 23 and the first head support 18 are constantly pulled in a predetermined direction by the action of the tension spring 39. The front panel 3 is provided with an opening 3b through which a synthetic resin knob 40 for actuating the eject lever 9 is projected and retracted. The knob 40 is secured to the front end of the eject lever 9 by a screw or other fixing means. The position sensor 32 is secured to the chassis 1 by a screw 41. The mounting plate 28c of the driving device 28 is secured to the chassis 1 by screws 42 which are respectively received by screw bores 42a. The first head support 18 is fastened to the carrier 27 by a screw 43 which is received through a mounting bore 27b provided at the front end portion of the carrier 27 so that the first head support 18 is prevented from pivoting with respect to the carrier 27. The carrier 27 is provided with a through-hole 27c for receiving the guide member 26. The first head support 18 is integrally formed with a pivot 18c which abuts against the central portion of the gimbals 19. The second head support 21 is also integrally formed with a pivot 21e which abuts against the central portion of the gimbals 22. The second head support 21 is formed with a cylindrical portion 21f on which is mounted the lower end of the coiled spring 31a of the spring device 31, and an opening 21g for receiving the terminal plate 35. The mounting member 31b of the spring device 31 is formed with a cylindrical portion 31d on which is mounted the upper end of the coiled spring 31a of the spring device 31. The chassis 1 is provided with a recess 1d for receiving the lower end portion of the carrier 27. The size of the recess 1d is set such that the carrier 27 moving on the guide member 26 does not collide with any edge portion of the recess 1d. A printed board (not shown) is disposed on the reverse surface of the chassis 1. The chassis 1 is provided with bores 1e and 1f for allowing connection between the electrical members on the chassis 1 and electrical parts mounted on the printed board. The bore 1e is employed for receiving a connector for the head cords 37 and 38, while the bore 1f is employed to connect terminals pins 32a of the position sensor 32 to corresponding electrical parts on the printed boared. The eject lever 9 is provided at its rear end with an automatic ejection mechanism 44. The holder 6 is provided with leaf springs 45 and 45a for guiding the cartridge 5 and leaf springs 46 and 46a which abut against the cartridge 5 when it is set inside the holder 6 such as to press the cartridge 5 in a predetermined direction. A cover 47 made from steel sheet is provided above the holder 6. A projection 1g for positioning the cover 47 is provided on the chassis 1. The cover 47 is provided in its central portion with a deformation preventing pin 48 which is constituted by a screw or other similar means. Should the cover 47 become slightly warped as the result of application of a strong force, the deformation preventing pin 48 abuts against the holder 6, thereby preventing permanent deformation of the cover 47. Further, the mounting plate 28c of the driving device 28 is so formed as to have an upper end contacting with the inner face of the cover 47 for preventing the deformation thereof. The holder 6 is provided with an opening 6a for receiving the second head support 21, relief bores 6b for preventing any rise in temperature of the magnetic disk 4, and an actuating member 6c which actuates the arm 33. A bent rib 6d is formed along the edge of the opening 6a. The bent rib 6d increases the strength of the holder 6 and offers electric and magnetic shielding effects for the second magnetic head 20. A shutter 49 is provided in the opening 3a of the front panel 3. When no cartridge 5 is loaded in the holder 6, the shutter 49 is closed so as to prevent intrusion of dust into the holder 6 or other portions from the opening 3a. The second head support 21 is provided with a notch 21h for positioning the arm 33. A relief recess 1h and a relief bore 1i are formed in the portion of the chassis 1 where the motor 28a is mounted. The arm 33 is integrally formed with a pin 33a. A cord retainer for the head cord 38 is formed by making use of the pin 33a and the arm 33. In the above-described arrangement, the arm 33 is normally raised by the actuating member 6c of the holder 6 and, consequently, the second head support 21 is swung upwardly, whereby collision between the first and second magnetic heads 17, 20 is prevented. When the cartridge 5 is inserted into the holder 6 from the opening 3a of the front panel 3 until the rear end portion of the cartridge 5 abuts against the lever 11a, the engagement between the lever 11a and the eject lever 9 is cancelled, and the eject lever 9 is moved forwardly by the action of the coiled spring 10. Consequently, the holder 6 as a wohle is lowered by the cooperation between the guide grooves 9c and the corresponding rollers 8. When the holder 6 is lowered, the hub 4a of the magnetic disk 4 is mounted on the hub holder 16, and the first and second magnetic heads 17, 20 are allowed to abut against the corresponding sides of the magnetic disk 4. Under this state, the motor 28a is actuated such as to rotate the lead screw 28b. Thereupon, the screw nut 28d held by the coupling member 23 moves on the lead screw 28b, causing the coupling member 23, the first head support 18, the carrier 27 and the second head support 21 to move along the guide member 26. According to this embodiment, the first head support 18 and the coupling member 23 are made of a metal, and the coupling member 23 is directly connected to the lead screw 28b. For this reason, the first head support 18 involves substantially no expansion and contraction as the result of fluctuations in temperature and relative humidity nor deformation with time and therefore suffers extremely small displacement with environmental change after the production thereof. Accordingly, it is possible for the first head support 18 to maintain its initial operation performance. Further, the carrier 27 formed with the through-hole 27c for receiving the guide member 26 is constituted by a molded product of a synthetic resin and it is therefore possible to carry out mass-production. Since the second head support 21 is also made of a metal, the second head support 21 is hardly expanded or contracted at all as the result of fluctuations in temperature and relative humidity, nor is it deformed with time. In consequence, the second head support 21 suffers extremely small displacement with environmental change after the production thereof and it is therefore able to maintain its initial operation performance in a manner similar to that of the first head support 18. Moreover, since the first and second head supports 18, 21 are both made of a suitable metal, they offer electric and magnetic shielding effects with respect to the first and second magnetic heads 17, 20. It is possible for a shielding member for the first and second magnetic heads 17, 20 to be integrally provided with the first or second head support 18 or 21, and there is no need to provide a shielding member as a separate member. It is therefore possible to greatly increase the degree of design freedom. Furthermore, the first and second head support 18, 21 and the gimbals 19, 22 are respectively welded together. Therefore, in the service environment (a temperature range between 5° and 45°; a humidity range between 30% and 80%), the first and second head supports 18, 21 thus welded display small displacement as the result of environmental change and therefore are able to maintain their initial operation performances. According to this embodiment, the metallic distant pieces 30 are respectively provided in the through-holes 27a of the carrier 27 by insert molding or press fitting in order to prevent any displacement between the first and second magnetic heads 17, 20 which would be caused by the reduction in the tightening force of the screws 29 as the result of the compressive deformation of the carrier 27 which may occur when the first head support 18, the synthetic resin carrier 27 and the second head support 21 are fastened together by the screws 29. Accordingly, even if the carrier 27 is made of a synthetic resin, it is possible for the first and second magnetic heads 17, 20 to be aligned with each other with high accuracy. Although in this embodiment each of the first and second head supports 18, 21 is formed by blanking a thin steel sheet, the first and second head supports 18, 21 possess sufficiently high rigidity since they are respectively provided with the bent pieces 18a and 21c. There is therefore no fear of the first and second head supports 18, 21 becoming curved in normal service conditions. Moreover, since the bent pieces 18a and 21c are formed such as to project from the respective surfaces of the first and second head supports 18, 21 which are opposite to the surfaces on which the first and second magnetic heads 17, 20 are mounted, it is possible to set a small gap between the first and second head supports 18, 21, which fact permits reduction in the thickness of the apparatus as a whole. Additionally, in this embodiment the mounting position of the arm 33 and the pressing position of the coiled spring 31a of the spring device 31 are located in a substantially straight line extending in a direction orthogonal to the longitudinal direction of the second head support 21. For this reason, when the second head support 21 is swung upwardly, there is no possibility of the second head support 21 being curved and permanently deformed. It is therefore possible to prevent any displacement between the first and second magnetic heads 17, 20. As has been described above, the magnetic head positioning apparatus according to the present invention includes the chassis, the driving device provided on the chassis, the guide member provided on the chassis, the carrier movably provided on the guide member, the first metallic head support mounted on the carrier and adapted to support the first magnetic head, the second metallic head support mounted on the carrier and adapted to support the second magnetic head which is disposed such as to oppose the first magnetic head, and the coupling member formed on the first head support as well as directly connected to the driving device, the coupling member being moved by the driving device in such a manner as to move the carrier along the guide member through the first head support. It is therefore possible to obtain a magnetic head positioning apparatus which has excellent resistance to environmental changes and is capable of positioning magnetic heads with high accuracy.

Claims: A magnetic head positioning apparatus for a magnetic disk (4) comprising: first and second magnetic heads (17, 20); first and second metal head supports (18, 21) on which the first and second magnetic heads (17, 20) are respectively mounted such that the second magnetic head (20) is opposed to the first magnetic head (17), the supports (18, 21) extending in a radial direction of the magnetic disk (4); means (27) for carrying the first and second head supports (18, 21) said carrying means (27) being made separately from said head supports (18, 21); and a guide member (26) on which the carrying means (27) is movably mounted; said guide member extending along a radial direction of the magnetic disk (4); characterized in that the apparatus comprises a chassis on which the guide member (26) is mounted and driving means (28) mounted on said chassis and coupled to one of said head supports (18) so as to move said magnetic heads (17, 20) through driving of said first and second head supports by said driving means while making said carrying means (27) follow therewith along said guide member (26), whereby said magnetic heads (17, 20) are accurately positioned with respect to each other without direct influence of said carrying means (27) in a direction of movement of said magnetic heads. An apparatus according to Claim 1 characterized in that said carrying means (27) is made of synthetic resin. An apparatus according to Claim 1 or 2 characterized in that said head supports (18, 21) are formed from sheet metal. An apparatus according to any one of Claims 2 to 3, characterized in that a metal coupling member (23) is provided on one (18) of said head supports (18, 21), and said driving means (28) and said one (18) of said head supports (18, 21) are coupled through said coupling member (23). An apparatus according to Claim 4, characterized in that said driving means (28) comprises a motor (28a) and a lead screw (28b) adapted to be rotated by said motor, and that said lead screw (28b) and said coupling member (23) are coupled to each other. An apparatus according to any one of Claims 1 to 5 characterized in that the head support (21) that is opposed to the head support (18) coupled to the driving means (28) is swingable with respect to said carrying means (27).

Inventors: HAYASHI, SEIICHI, SEKI, GEN
Applicants: HITACHI, LTD.
Application year: 1985
Main classification: G11B5
IPC codes: G11B5