LINEAR MOTOR LOCKING MECHANISM IN A DISC UNIT

Abstract: A linear motor (3) is movably disposed in a disc unit (1) internally provided with a loading device (11) for loading and ejecting a disc cartridge (10) and is securely locked by a locking mechanism at the time of ejection of the cartridge (10). The locking mechanism comprises a first locking member (12) extending downwards from the loading device (11) and a second locking member (9) securely mounted on the linear motor (3). When the disc cartridge (10) is ejected by the loading device (11), the first locking member (12) is brought into contact with the second locking member (9) to move the linear motor (3) towards a location at which the linear motor (3) is securely locked.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a linear motor locking mechanism in a disc unit employing therein a photomagnetic disc or the like. Such a mechanism can prevent an optical pickup mounted on the linear motor from being damaged by making the linear motor unmoved when the disc unit is moved. Description of the Prior Art A linear motor movably disposed in a disc unit is usually kept unmoved when the disc unit is moved from one location to another. If the linear motor is left free without being locked, it would occasionally strike a frame. Accordingly, there is the danger of destroying an optical pickup provided on the linear motor. Figs. 1 and 2 depict conventional mechanisms for locking the linear motor. In the mechanism as shown in Fig. 1, a special purpose locking bar 2 is inserted into a disc unit 1 from behind and pushes a linear motor 3 accommodated in the disc unit 1 against a frame 4 to lock it. The mechanism of Fig. 2 employs a locking cartridge 6 provided with a biasing member 5. In this mechanism, when the locking cartridge 6 is brought into operation, the biasing member 5 depresses the linear motor 3 from above to lock it. Furthermore, a mechanism (not shown) employing an electric actuator such as a solenoid or the like has been proposed, in which the actuator is brought into contact with the linear motor to lock it when a power source is switched off. Other mechanisms are known from US-A-4 472 796 and US-A-4 574 372. However, these mechanisms inevitably require such elements as the special purpose lock bar 2 for exclusive use, the locking cartridge 6 or the like, thus increasing the number of parts. Accordingly, such mechanisms are disadvantageous in that they are relatively costly and troublesome in management. Besides, the conventional mechanisms include the danger of damaging the disc unit by switching on the power source when the linear motor is locked. SUMMARY OF THE INVENTION Accordingly, the present invention has been developed with a view to substantially eliminating the above described disadvantages inherent in the prior art mechanism for locking a linear motor, by providing an improved mechanism which is simple in construction and stable in functioning and is capable of locking the linear motor without the use of any specialized locking member and never permits the linear motor to be in an unlocked condition at the time of ejection of a disc cartridge. To accomplish these objects, the present invention provides a mechanism for locking a linear motor movably disposed in a disc unit which is internally provided with a loading device for loading and ejecting a disc cartridge, characterised in that said mechanism comprises a first locking member extending downwards from the loading device; and a second locking member securely mounted on the linear motor; said first locking member, when the disc cartridge is ejected by the loading device, being brought into contact with said second locking member to move the linear motor towards a location at which the linear motor is locked. By the above described construction, the linear motor is securely locked inside the disc unit at the time of ejection of the disc cartridge without the need of any special purpose locking part. The present invention also provides a disc unit including a linear motor for driving a head of the unit and a loading device for loading and ejecting a disc member to and from the unit, characterised in that said loading device is arranged to move a moveable component of the linear motor to a locked position when it ejects the disc member. BRIEF DESCRIPTION OF THE DRAWINGS These and other objects and features of the present invention will become more apparent from the following description taken in conjunction with the preferred embodiment thereof with reference to the accompanying drawings, throughout which like parts are designated by like reference numerals, and wherein; Fig. 1 is a schematic sectional view of a disc unit provided with a conventional mechanism for locking a linear motor movably disposed therein; Fig. 2 is a view similar to Fig. 1, indicative of another conventional locking mechanism; Fig. 3 is a schematic sectional view of the disc unit accommodating a linear motor locking mechanism according to one preferred embodiment of the present invention; and Fig. 4 is a view similar to Fig. 3, which particularly shows an activated condition of the mechanism of Fig. 3. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 3 depicts a disc unit 1 internally provided with a linear motor locking mechanism according to one preferred embodiment of the present invention. The disc unit 1 accommodates a frame 4 fixedly mounted therein, a linear motor 3 movably disposed on the frame 4, an optical pickup 7 securely mounted on the upper surface of the linear motor 3, a magnetic circuit 8 fixedly mounted on the frame 4 behind the linear motor 3 and a loading device 11 movably disposed above the frame 4. The linear motor 3 is provided on its upper surface behind the optical pickup 7 with a locking member 9. A disc cartridge 10 is loaded in and ejected from the disc unit 1 by the loading device 11, which is provided on its rear side with a locking member 12 extending downwards therefrom. As shown in Fig. 3, when the disc cartridge 10 is loaded in the disc unit 1 by the loading device 11 and properly positioned therein, the locking member 12 thereof is located behind and in contact with the locking member 9 of the linear motor 3. In the above described construction, when the disc cartridge 10 is ejected from the disc unit 1, the loading device 11 advances outwards. In this event, the locking member 12 which extends downwards from the rear end of the loading device 11 and is in contact with the locking member 9 of the linear motor 3 advances the linear motor 3. When the loading device 11 has reached an ejection position at which it can eject the disc cartridge 10 from the disc unit 1, the front surface 3a of the linear motor 3 is brought into contact with a surface of the frame 4 confronting it, as shown in Fig. 4. In this event, a portion of the linear motor 3 is sandwiched between the frame 4 and the locking member 12 of the loading device 11 so that the linear motor 3 may be locked. Accordingly, the linear motor 3 is always locked and kept unmoved at the time of ejection of the disc cartridge 10. When the disc cartridge 10 is loaded in the disc unit 1, the loading mechanism 11 moves backwards inside the disc unit 1. Consequent upon this, since the locking member 12 moves backwards at the same time, the linear motor 3 is released from its locked condition. As is clear from the above, the locking mechanism according to the present invention never requires any specialized mechanism or any part for exclusive use because the linear motor is locked by making use of the loading device. In other words, the number of parts is reduced and only the locking members of extremely simple construction are additionally provided in the unit. As a result, not only can the production cost be reduced but troublesome management will hardly be required. Furthermore, when the disc cartridge is ejected from the unit, the linear motor is locked without fail. Accordingly, the linear motor will never be left free and the optical pickup can be prevented from being damaged by the movement of the linear motor.

Claims: A mechanism for locking a linear motor (3) movably disposed in a disc unit (1) which is internally provided with a loading device (11) for loading and ejecting a disc cartridge (10), characterized in that said mechanism comprises: a first locking member (12) extending downwards from the loading device (11); and a second locking member (9) securely mounted on the linear motor (3); said first locking member (12), when the disc cartridge (10) is ejected by the loading device (11), being brought into contact with said second locking member (9) to move the linear motor (3) towards a location at which the linear motor (3) is locked. The mechanism according to claim 1, wherein a portion of said linear motor (3) is sandwiched between a frame (4) fixedly mounted in the disc unit (1) and said first locking member (12) in contact with said second member (9), when said linear motor (3) is locked at said location. A disc unit (1) including a linear motor (3) for driving a head (7) of the unit and a loading device (11) for loading and ejecting a disc member (10) to and from the unit, characterised in that said loading device is arranged to move a moveable component of the linear motor to a locked position when it ejects the disc member.

Inventors: HORIGUCHI, AKIO, HORII, MASAHIRO, TAKEMOTO, TETSUYUKI, TANIGUCHI, SHOJI
Applicants: SHARP KABUSHIKI KAISHA
Application year: 1989
Main classification: G11B17
IPC codes: G11B19, G11B17, G11B7, G11B21