Magnetic head holding apparatus for recording a magneto-optical disc

A magneto-optical disc recording and/or reproducing apparatus for writing in and/or reading out an information signal from a rewritable magneto-optical disc is provided. In particular, a lifting mechanism for lifting a supporting arm that supports the magnetic head is provided where a lifting member is interposed between an arm member supporting a magnetic head and a magneto-optical disc. The lifting member is supported by a chassis in a manner in which it is rotatable in a direction in which it allows the magnetic head to come into contact with or near to a magneto-optical disc surface and in an opposite direction away from the magneto-optical disc.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention generally relates to magneto-optical disc recording
 and/or reproducing apparatus for writing in and/or reading out an
 information signal from a rewritable magneto-optical disc and, more
 particularly, is directed to a lifting mechanism for lifting a supporting
 arm that supports thereon a magnetic head which generates an external
 magnetic field to a magneto-optical disc.
 2. Description of the Related Art
 It is customary that a magnetic head for a rewritable magneto-optical disc
 (hereinafter simply referred to as an MO disc) is located as close as
 possible to the MO disc in order to generate a sufficient external
 magnetic field to the surface of the MO disc when an information signal is
 recorded on the MO disc. Therefore, when the MO disc is loaded onto and/or
 ejected from the magneto-optical disc recording and/or reproducing
 apparatus, the magnetic head must be isolated from the MO disc so that the
 MO disc is prevented from coming in contact with the magnetic head. A
 mechanism for lifting an arm that supports the magnetic head is therefore
 used to isolate the magnetic head from the MO disc. The conventional arm
 lifting mechanism is generally composed of an arm supporting mechanism and
 an actuator such as a plunger or the like secured to one portion of the
 arm supporting mechanism.
 Since, however, the arm supporting mechanism has little space to spare, the
 above arm lifting mechanism cannot be incorporated into the small space
 substantially from a technical standpoint. Further, the arm supporting
 mechanism has mounted thereon a relatively heavy actuator because it is
 coupled to the moving mechanism of an optical pickup device. Therefore,
 the load is increased and a drive motor suffers from the increased load so
 that the conventional arm supporting mechanism is not suitable for
 reducing an amount of electric power. To solve the above problem, it is
 proposed that the actuator is supported to a stationary member such as a
 chassis or the like that is not operated in a ganged relation with the arm
 supporting mechanism. However, an arm itself is operated in a ganged
 relation with the optical pickup device and the arm is moved in the inner
 and outer diametrical directions of the MO disc during an information
 signal is written in and/or read out from the MO disc. There is then the
 problem such that an undesirable load is applied to the arm by the
 actuator.
 OBJECTS AND SUMMARY OF THE INVENTION
 Therefore, it is an object of the present invention to provide an improved
 magnetic head supporting arm lifting mechanism in which the aforesaid
 shortcomings and disadvantages of the prior art can be eliminated.
 It is an object of the present invention to provide a magnetic head
 supporting arm lifting mechanism in which an arm having mounted thereon a
 magnetic head can be smoothly lifted without a load applied thereto by an
 arm lifting mechanism.
 It is another object of the present invention to provide a magnetic head
 supporting arm lifting mechanism that can be simplified in arrangement.
 It is still another object of the present invention to provide a magnetic
 head supporting arm lifting mechanism in which an arm can be lifted in a
 small space, thereby making a magneto-optical disc recording and/or
 reproducing apparatus compact in size.
 According to an aspect of the present invention, there is provided a
 magnetic head supporting mechanism for a magneto-optical disc recording
 and/or reproducing apparatus which includes an optical pickup device being
 made movable in the radial direction of a magneto-optical disc and
 radiating a light beam on tracks formed on the magneto-optical disc, and a
 magnetic head disposed on a head supporting mechanism movable in
 synchronism with the optical pickup device in an opposing relation to the
 optical pickup device across the magneto-optical disc so that the magnetic
 head generates an external magnetic field on the tracks of the
 magneto-optical disc. This magnetic head supporting mechanism comprises an
 arm member having on one end thereof provided the magnetic head and being
 rotatably supported by a movable member that is moved in synchronism with
 the optical pickup device in the direction in which the magnetic head
 comes in contact with or away from a surface of the magneto-optical disc,
 a lifting member being interposed between the arm member and the
 magneto-optical disc in substantially parallel to the moving direction of
 the magneto-optical disc and being supported at least on one end thereof
 to a chassis so that the lifting member becomes rotatable in the direction
 in which it comes in contact with or away from the surface of the
 magneto-optical disc surface, and a driving device for rotating the
 lifting member so that the arm member is lifted in the direction in which
 the arm member comes away from the surface of the magneto-optical disc.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The present invention will now be described in detail with reference to the
 drawings.
 FIG. 1 of the accompanying drawings shows a perspective view of a main
 portion that constructs a rewritable magneto-optical disc recording and/or
 reproducing apparatus. FIG. 2 of the accompanying drawings shows a
 perspective view of a lifting mechanism for a magnetic head supporting
 arm.
 As illustrated, the MO (magneto-optical) disc recording and/or reproducing
 apparatus includes an optical pickup device 2 disposed on the rear surface
 side of a rewritable MO disc 1 and a magnetic head 3 disposed in an
 opposing relation to the optical pickup device 2 across the MO disc 1.
 The MO disc 1 is loaded onto a turntable (not shown) in the horizontal
 direction and sandwiched between the turntable 4 and a clamping plate 6
 attracted to the MO disc 1 by a magnet force of a magnet (not shown) that
 is provided on the turntable. The MO disc 1 thus held on the turntable is
 rotated by a spindle motor 7 that is directly coupled to the turntable.
 The optical pickup device 2 comprises an optical system 8 having a
 semiconductor laser and a variety of lenses, an objective lens 9 for
 radiating a converging laser beam on the MO disc 1 and a bi-axial device
 10 for moving the objective lens 9 in the tracking direction and/or
 focusing direction. As shown in FIG. 2, the optical pickup device 2 thus
 arranged is supported horizontally by means of a lead screw shaft 12 that
 is supported by bearing portions 11a, 11b and a guide shaft 13 which is
 also supported in a bearing fashion. That is, when a pulley 14 provided on
 one end of the lead screw shaft 12 is rotated by a drive motor 15 via a
 belt 16, the lead screw shaft 12 is rotated and hence the optical pickup
 device 2 is fed by the lead screw shaft 12 so as to become movable along
 the guide shaft 13 in the inner and/or outer diametrical direction of the
 MO disc 1.
 The magnetic head 3 is disposed on an arm mechanism 17 that is moved in the
 inner and/or outer diametrical direction of the MO disc 1 in synchronism
 with the optical pickup device 2.
 A magnetic head supporting arm and a lifting mechanism for this supporting
 arm, each of which is a main portion of the present invention, will be
 described in detail below with reference to FIG. 3 of the accompanying
 drawings.
 As shown in FIG. 3, the arm mechanism 17 comprises an arm member 18 and an
 arm supporting member 19. The arm member 18 is formed of a hard
 plate-shaped member of plastic material such as nylon resin or the like. A
 rear portion of the arm member 18 is molded as one body with a coupling
 member 20 serving as a moving member to thereby form a U-letter shape
 together with the optical pickup device 2. The arm member 18 is moved in a
 ganged relation with the optical pickup device 2. The arm member 18 is
 swingably rotated in the upper and lower direction by a resilient
 displacing portion 21 that is formed thin in the upper and lower direction
 as compared with the coupling member 20. On the front end portion of the
 arm member 18, there is provided the magnetic head 3 in an opposing
 relation to the objective lens 9 of the optical pickup device 2. A sliding
 member 22 including a spherical contact surface 23 that comes in contact
 with the surface of the MO disc 1 is attached to the arm member 18 at its
 portion near the magnetic head 3.
 The arm supporting member 19 is formed of a metal member of a channel
 configuration. As shown in FIG. 3, the arm supporting member 19 comprises
 an attaching plate 24 elongated to the rear end side thereof, a spring
 supporting member 25 elongated horizontally from the upper edge to the
 front side and an arm stopper 26 elongated horizontally from the lower
 edge to the same direction as the direction in which the attaching plate
 24 is elongated.
 The arm member 18 and the arm supporting member 19 will be described more
 fully. The attaching plate 24 of the arm supporting member 19 is secured
 to the upper surface of the coupling member 20 by screws 27 and the arm
 member 18 is supported on the arm stopper 26 of the arm supporting member
 19. The arm member 18 is downwardly spring-biased by a coil spring 29
 interposed between a concave portion 28 formed thereon and the spring
 support 25 of the arm supporting member 19.
 The structure of the arm lifting mechanism will be described below.
 As shown in FIGS. 1 and 2, a lifting member 30 of a rod configuration is
 disposed at the rear surface side of the arm mechanism 17. The lifting
 member 30 is disposed in parallel to the moving direction of the arm
 mechanism 17 and is sufficiently long so that it can traverse the tracks
 of the MO disc 1. Ends of links 31, 32 are secured to respective ends of
 the lifting member 30 by screws. These links 31, 32 are fixed at their
 other ends to hinge portions 35, 35 that are respectively supported to
 bearing portions 34, 34 of a chassis 33 serving as a fixed frame of the
 apparatus. One link 31 includes a curved lever 36 of substantially
 L-letter configuration and the lever 36 is coupled to a rod 38 of a
 plunger mechanism 37 attached on the chassis 33. Thus, the arm lifting
 mechanism is constructed.
 According to the arm lifting mechanism, when the plunger mechanism 37 is
 energized to move the rod 38 in the rearward due to an exciting action,
 the lifting member 30 is upwardly rotated about the hinge portions 35, 35
 together with the links 31, 32 through the lever 36. Therefore, the arm
 member 18 of the arm mechanism 17 is pushed upwardly against the spring
 force of the coil spring 29 interposed between the concave portion 28 and
 the arm supporting member 19 by the lifting member 30 so that the arm
 member 18 can be lifted upwardly about the resilient displacement portion
 21.
 After the arm member 18 was lifted upwardly, the plunger mechanism 37 is
 disabled and the rod 38 is moved forward by the spring action, whereby the
 lifting member 30 is downwardly rotated about the hinge portions 35, 35
 together with the links 31, 32 in a manner opposite to the above
 operation. Consequently, the arm member 18 is released from being pushed
 upwardly by the lifting member 30 so that the arm member 18 is returned to
 the original position by the spring-biasing force of the coil spring 29.
 During the MO disc recording and/or reproducing apparatus having the arm
 lifting mechanism writes and/or reads an information signal in and/or from
 the MO disc 1, the sliding member 22 provided on the arm member 18 is
 brought in contact with the surface of the MO disc 1. In that case, the
 arm member 18 is floated from the arm stopper 26 of the arm supporting
 member 19 so that the sliding member 22 is urged against the surface of
 the MO disc 1 only by a pressing force of the spring-biasing force of the
 coil spring 29.
 Under the condition such that the sliding member 22 is brought in contact
 with the surface of the MO disc 1, the write and/or read operation is
 carried out by the optical pickup device 2 and the magnetic head 3 while
 the tracks of the MO disc 1 are being traced by the optical pickup device
 2 and the magnetic head 3. Therefore, the optical pickup device 2 and the
 magnetic head 3 are unitarily moved from the inner diameter to the outer
 diameter of the MO disc 1. Then, the arm mechanism 17 that is moved in
 synchronism with the optical pickup device 2 is moved along the direction
 in which the lifting member 30 is disposed. The lifting member 30 is
 therefore constantly located under the arm mechanism 17 and the plunger
 mechanism 37 serving as the actuator of the lifting member 30 is attached
 on the chassis 33 such that the plunger mechanism 37 does not hinder the
 movement of the arm mechanism 17. Therefore, even if the optical pickup
 device 2 and the magnetic head 3 are located at either the outermost end
 or innermost end of the MO disc 1, the arm member 18 can be reliably
 lifted by the lifting member 30 when the MO disc 1 is loaded and/or
 ejected from the MO disc recording and/or reproducing apparatus.
 Since the plunger mechanism 37 is disposed on the chassis 33 that serves as
 the fixed frame, the load on the drive motor can be reduced as compared
 with the conventional method in which the plunger mechanism is mounted on
 the moving member that moves in a ganged relation with the optical pickup
 device. In addition, a freedom in design that the plunger mechanism 37 is
 mounted on the chassis 33 can be increased considerably. Further, since
 the lifting member 30 is of the rotating type such that is can be rotated
 about the hinge portion 35, a wide space for rectilineally moving the
 lifting member 30 is not needed and a small space is sufficient.
 Therefore, the lifting mechanism can be designed compact and simplified in
 arrangement.
 FIGS. 4 and 5 of the accompanying drawings show the arm lifting mechanism
 according to second and third embodiments of the present invention,
 respectively.
 In the arm lifting mechanism shown in FIG. 4, a lifting member 39 is
 manufactured from a metal material. Hinge shafts 40, 40 are eccentrically
 formed on side edges of the respective ends of the lifting member 39, and
 a lever plate 41 is recessed and raised vertically from the lifting member
 39 near one hinge shaft 40. A flange 42 is formed on the lifting arm
 member 39 at its side edge opposing the hinge shafts 40, 40 through a
 curved surface 39a.
 In the above arm lifting mechanism, the hinge shafts 40, 40 of the lifting
 member 39 are rotatably supported on the bearing portions 34, 34 provided
 on the chassis 33 that was described in the first embodiment, and the
 lever plate 41 is coupled to the rod of the plunger mechanism (not shown).
 That is, when the rod is moved forwardly or backwardly, the lifting member
 39 is rotated about the hinge shafts 40, 40 through the lever plate 41 and
 the arm member 18 (see FIG. 2) is lifted by the curved surface 39a of the
 lifting member 39. Therefore, the lifting member 39 is molded by one
 member and can be produced inexpensively. Moreover, since the arm member
 18 is lifted with a pressure by the curved surface 39a, the arm member 18
 can be lifted smoothly. Further, since the flange 42 is formed on the
 outer edge of the curved surface 39a, the arm member 39 can be increased
 in rigidity.
 FIG. 5 of the accompanying drawings shows the third embodiment of the arm
 lifting mechanism that is molded from a plastic material. As shown in FIG.
 5, a lifting member 43 has formed on one side edge portion thereof,
 supporting portions 45, 45 coupled to the lifting member 43 through thin
 resilient displacement portions 44, 44 serving as hinge portions. Also,
 the lifting member 43 has formed on the other side edge portion thereof a
 spherical surface portion 46. A lever plate 47 is formed on one end
 portion of the lifting member 43.
 In the arm lifting mechanism thus arranged, the supporting portions 45, 45
 are secured to the chassis 33 shown in FIG. 4 and the lever plate 47 is
 coupled to the rod of the plunger mechanism, also not shown. According to
 the third embodiment of the arm lifting mechanism, when the rod is moved
 forwardly or backwardly, moving the lever plate 47, the lifting member 43
 displaces the resilient displacement portions 44, 44. The arm member (not
 shown in FIG. 5) is lifted by the spherical portion 46 with the relative
 angular displacement of the lifting member 43 with respect to the
 supporting portions 45. Therefore, since the lifting member 43 can be
 molded in one molding process, the lifting mechanism can be made
 inexpensive. Furthermore, since the arm member is lifted by the spherical
 portion 46 of the lifting member 43, the arm member can be lifted
 smoothly.
 While the arm mechanism 17 is of the type such that it is brought in
 contact with the MO disc as described above, the present invention is not
 limited thereto and may be applied to the case such that the magnetic head
 3 is of the non-contact type that is servo-controlled by the actuator.
 Furthermore, while the present invention is applied to the MO disc
 recording and/or reproducing apparatus which records and/or reproduces the
 MO disc under the condition that the MO disc is held in the horizontal
 direction as described above, the present invention is not limited thereto
 and may be applied to an MO disc recording and/or reproducing apparatus
 which records and/or reproduces the MO disc under the condition such that
 the MO disc is held in the vertical direction.
 Having described preferred embodiments of the invention with reference to
 the accompanying drawings, it is to be understood that the invention is
 not limited thereto and that various changes and modifications could be
 effected therein by one skilled in the art without departing from the
 spirit or scope of the invention as defined in the appended claims.