Method of manufacturing a magnetic disc cartridge

Abstract: A method of manufacturing a magnetic disc cartridge comprising a casing formed of upper and lower shell halves mated together, a disc-like recording medium supported for rotation in the casing and a liner fixed to each of the inner surfaces of the upper and lower shell halves, in which method the surface of an edge portion of the liner facing the recording medium is made more distant from the recording medium than the other part of the liner and fixing agent is caused to soak into the edge portion and is solidified there.

Description: Field of the Invention This invention relates to a method of manufacturing a magnetic disc cartridge according to the pre-characterizing part of claim 1. Background of the Invention In a magnetic disc cartridge comprising a disc-like recording medium supported for rotation in a casing formed of upper and lower shell halves, a pair of liners formed of nonwoven fabric or the like are generally fixed to the inner surfaces of the upper and lower shell halves, respectively. The liners are for protecting the recording medium and are formed of nonwoven fabric or the like of rayon or the like in a predetermined shape. The liners are fixed to the inner surfaces of the upper and lower shell halves by welding such as ultrasonic welding. Each liner is generally octagonal in contour and is provided with a central opening and a slit-like cutaway portion which is opposed to the magnetic head insertion opening formed in the corresponding shell half. When welding the liner to the shell half, a welding horn is pressed against the liner placed on the inner surface of the shell half and heat or ultrasonic vibration is applied to the welding horn, thereby fusing the inner surface of the shell half to the liner. For example, there has been proposed in Japanese Patent Application No. 9(1997)-296838, a method of fixing a liner to the inner surface of a shell half by ultrasonic welding in which an energy director in the form of a protrusion is formed in a predetermined pattern on the inner surface of the shell half, the liner is placed on the energy director, and an ultrasonic welding horn is pressed against the liner so that the energy director is fused to the liner. In the past, the liner is fixed to the shell half only at a part of its peripheral edge. Accordingly the non-fixed part of the peripheral edge and/or the central portion of the liner is in a floating condition and can be brought into contact with the recording medium. However, recently, as the recording capacity of the recording medium increases, it becomes necessary to rotate the recording medium at a higher speed. When the recording medium rotated at a high speed is constantly in contact with the liner, contaminants can be produced, for instance, by separation of fibers from the liner. When such contaminants adhere to the recording medium and/or the magnetic head, recording and reproducing performance can be adversely affected, recording medium driving torque can be increased, and the recording medium can wobble during rotation. Accordingly, there is a tendency to reduce contact of the liner to the recording medium. Further since the liner is stamped out from a sheet of unwoven fabric, when the liner is not welded over its entire peripheral edge, cut fibers can drop from its peripheral edge and can adhere to the surface of the recording medium to cause drop out. Further since the liner is formed of a hygroscopic material such as rayon, when the central portion of liner is not fixed to the inner surface of the shell half, the liner is deformed in such a manner that the central portion bulges upward due to hygroscopicity under the conditions of 60° C in temperature and 90% in humidity. When the liner is thus deformed, the bulging portion is brought into contact with the recording medium which rotating at a high speed, which gives rise to the aforesaid problems. In accordance with the pre-characterizing art of claim 1 US-A-5 705 004 discloses a method of manufacturing a magnetic disc cartridge in which the surface of each liner is flat within the entire area thereof, i.e. the upper and lower surface of the lower and upper liner each lie within the same plane. Summary of the Invention In view of the foregoing observations and description, the primary object of the present invention is to provide a method of manufacturing a magnetic disc cartridge which can prevent fibers from dropping from the peripheral edges of the liners and can prevent the liners from constantly contacting with the rotating recording medium. This is achieved by the features of claim 1. Preferred embodiments are defined by the dependent claims. In accordance with the present invention, the surface of an edge portion of the liner facing the recording medium is made more distant from the recording medium than the other part of the liner and fixing agent is caused to soak into the edge portion and is solidified there. The surface of an edge portion of the liner facing the recording medium may be made more distant from the recording medium than the other part of the liner, for instance, by forming a recess in the inner surface of the shell half or by compressing the part of the liner with the inner surface of the shell half held flat. The fixing agent may be adhesive applied to the liner or may be molten resin obtained.by fusing the shell half by applying heat or ultrasonic vibration. Brief Description of the Drawings Figure 1 is an exploded perspective view of a magnetic disc cartridge manufactured by a method in accordance with a first embodiment of the present invention, Figure 2 is a fragmentary cross-sectional view showing an important part of a magnetic disc cartridge manufactured by a method in accordance with an embodiment of the present invention, Figures 3A and 3B are views for illustrating an example of the method of bonding the liner to the shell half by use of adhesive in the embodiment, Figures 4A to 4C are views for illustrating another example of the method of bonding the liner to the shell half by use of adhesive in the embodiment, Figures 5A and 5B are views for illustrating still another example of the method of bonding the liner to the shell half by use of adhesive in the embodiment, Figures 6A to 6C are views for illustrating still another example of the method of bonding the liner to the shell half by use of adhesive in the embodiment, Figures 7A and 7B are views for illustrating an example of the method of bonding the liner to the shell half by welding in the embodiment, Figures 8A and 8B are views for illustrating another example of the method of bonding the liner to the shell half by welding in the embodiment, and Figures 9A and 9B are views for illustrating examples of the protrusion pattern to be formed on the inner surface of the shell half. Preferred Embodiment of the Invention In Figure 1, a magnetic disc cartridge manufactured by a method in accordance with the present invention comprises a flat casing C formed of upper and lower shell halves 1 and 2 which are formed of synthetic resin such as acrylonitrile-butadiene-styrene copolymer. A recording medium (magnetic disc) 4 with a central core member 3 mounted on the center thereof is supported for rotation in the casing C. An upper liner 5 is fixed to the inner surface of the upper shell half 1 and a lower liner 6 is fixed to the inner surface of the lower shell half 2. The recording medium 4 comprises a flexible disc-like base formed of resin such as polyethylene terephtalate and magnetic layers formed on opposite sides of the base. Inner and outer peripheral edge portions of the recording medium 4 form a non-recording area 4b and the annular portion between the inner and outer peripheral edge portions forms a recording area 4a. The upper and lower shell halves 1 and 2 are flat and square in shape, and are provided with outer peripheral ribs 1a and 2a which form side walls of the casing C. Inner ribs 1b and 2b are formed to extend obliquely at each corner of the upper and lower shell halves 1 and 2 and magnetic head insertion openings 10 and 11 are formed in the respective shell halves 1 and 2. A spindle hole 2c through which a spipdle of a recording and reproducing system acts on the center core member 3 is formed in the lower shell half 2 at the center thereof. Though not shown, a shutter member is mounted on the casing C to be slidable left and right to close and open the magnetic head insertion openings 10 and 11. The upper and lower liners 5 and 6 are fixed by ultrasonic welding to inner surfaces of the upper and lower shell halves 1 and 2 inside the inner ribs 1b and 2b. The middle portion of each inner ribs 1b and 2b are curved to extend along the outer peripheral edge of the recording medium 4. An annular protrusion 12 extends downward from the inner surface of the upper casing half 1 at the center thereof and is fitted in the central core member 3 on the recording medium 4, thereby limiting movement of the recording medium 4 in the radial direction thereof relative to the casing C. The liners 5 and 6 are of the same shape and substantially octagonal in outer contour. Each liner is provided with a slit at a portion opposed to the magnetic head insertion opening (10 or 11) and a central opening which is slightly larger than the annular protrusion 12 or the spindle hole 2c. Each liner is formed of, for instance, unwoven fabric such as of a blend of rayon and PET or nylon. Unwoven fabric of a blend of continuous fibers of cotton cellulose (70%) and PET fibers (30%) is advantageous in that separation of fibers is less. Each of the upper and lower shell halves 1 and 2 is provided with an energy director 14 in the form of a protrusion formed on the inner surface of the shell half in a predetermined pattern. In the example shown in Figure 1, the pattern of the energy director 14 comprises an edge portion pattern formed of a protrusion extending along the outer peripheral edge, the inner peripheral edge and the linear edges of the slit of the liner and an inside pattern formed of a plurality of radial protrusions extending from the part of the edge portion pattern extending along the inner peripheral edge defining the central opening to the part of the same extending along the outer peripheral edge. The energy director 14 may be formed of a continuous protrusion which is triangular in cross-section or of a plurality of discontinuous protrusions. The radial protrusions in the inside pattern may be more densely formed or less densely formed though it is preferred that they are arranged at substantially regular intervals in the circumferential direction. The liners 5 and 6 are fixed to the inner surfaces of the respective shell halves 1 and 2 by ultrasonic welding by use of an ultrasonic welding horn having a welding face which is octagonal in outer contour. The welding face is substantially the same as the liners 5 and 6 in shape and dimensions. That is, the welding face of the ultrasonic welding horn is substantially octagonal in outer contour and is provided with a central opening corresponding to the central opening of the liner. A method of manufacturing a magnetic disc cartridge in accordance with an embodiment of the present invention will be described with reference to Figures 2 to 9B, hereinbelow. In this embodiment, the surface of the outer peripheral edge portion of each of the liners facing the recording medium 4 is made more distant from the recording medium 4 than the other part of the liner and fixing agent is caused to soak into the edge portion and is solidified there. Since the upper and lower liners 5 and 6 are fixed to the upper and lower shell halves 1 and 2 in the same manner, only the upper liner 5 will be described hereinbelow. As shown in Figure 2, the upper wall portion ld of the shell half 1 is provided with an annular recess le in its inner surface at a portion opposed to the outer peripheral edge portion 5a of the liner 5 and the outer peripheral edge portion 5a of the liner 5 is fixed to the bottom of the recess le so that the surface of the peripheral edge portion 5a facing the recording medium 4 is positioned more distant from the recording medium 4 than the other part of the liner 5. Further fixing agent S is caused to soak into the peripheral edge portion 5a and is solidified there. The difference h in level or distance from the recording medium 4 between the peripheral edge portion 5a and the other portion of the liner 5 is set to be 0.05 to 0.3mm. The level difference h may be made in various manners other than by forming a recess in the inner surface of the shell 1 as shown in Figure 2. For example, the level difference h may be made by compressing the outer peripheral edge portion of the liner 5 with the inner surface of the shell half 5 held flat. The fixing agent S may be adhesive applied to the liner or may be molten resin obtained by fusing the shell half by applying heat or ultrasonic vibration as will be described later. For example, when the fixing agent S is adhesive, an adhesive layer (e.g., ultraviolet-setting adhesive) 7 is formed on the bottom of the recess 1e and the liner 5 is placed on the inner surface of the shell half 1 as shown in Figure 3A. Then the outer peripheral edge portion 5a of the liner 5 is pressed against the adhesive layer 7, thereby deforming the liner 5 along the recess le and causing the adhesive 7 to soak into the peripheral edge portion 5a up to the surface facing the recording medium 4 as shown in Figure 3B. Then the adhesive 7 is solidified by exposing to ultraviolet rays. In the example shown in Figures 3A and 3B, the liner 5 is bonded to the shell half 1 only at its outer peripheral portion 5a. However the liner 5 may be bonded to the shell half 1 over the entire area thereof. In this case, in order to cause the adhesive to soak into the outer peripheral edge portion 5a, the amount of adhesive applied to the outer peripheral edge portion 5a is increased. For example, an adhesive layer 7 is formed on the bottom of the recess le in a predetermined thickness as shown in Figure 4A, and then another adhesive layer 7 is formed on the inner surface of the shell half 1 uniformly over the entire area of the liner 5 so that the thickness of the adhesive layer 7 becomes larger at the part opposed to the outer peripheral edge portion 5a of the liner 5 than the other part as shown in Figure 4B. Then the outer peripheral edge portion 5a of the liner 5 is pressed against the adhesive layer 7, thereby deforming the liner 5 along the recess le and causing the adhesive 7 to soak into the peripheral edge portion 5a up to the surface facing the recording medium 4 as shown in Figure 4C. Then the adhesive 7 is solidified by exposing to ultraviolet rays. Otherwise, an adhesive layer 7 may be formed at one time on the inner surface of the shell half 1 over the entire area of the liner 5 so that the thickness of the adhesive layer 7 becomes larger at the part opposed to the outer peripheral edge portion 5a of the liner 5 than the other part as shown in Figure 5A and 5B. Otherwise, an adhesive layer 7 is formed on the inner surface of the shell half 1 uniformly over the entire area of the liner 5 as shown in Figure 6A, and then the outer peripheral edge portion 5a of the liner 5 is pressed against the adhesive layer 7 so that the liner 5 is deformed along the recess le and another adhesive layer 7 is formed on the outer peripheral edge portion 5a of the liner as shown in Figure 6B. Then the adhesive layer 7 is caused to soak into the outer peripheral edge portion 5a of the liner as shown in Figure 6C. When molten resin obtained by fusing the shell half of ABS resin is used as the fixing agent S, the liner 5 is placed on the inner surface of the shell half 1 and a heater head (or an ultrasonic welding horn) 25 is pressed against the outer peripheral edge portion 5a of the liner 5 as shown in Figure 7A, thereby fusing the inner surface of the shell half 1 so that molten resin is caused to soak into the outer peripheral edge portion 5a. After the molten resin is solidified, the outer peripheral edge portion 5a of the liner 5 is partly embedded in the inner surface of the shell half 1 as shown in Figure 7B. When molten resin obtained by fusing the shell half is used as the fixing agent.S, a protrusion pattern 8 like an energy director which is used in ultrasonic welding may be formed on the bottom of the recess le as shown in Figure 8A. In this case, the protrusion pattern 8 is fused and the molten resin of the protrusion pattern 8 is caused to soak into the outer peripheral edge portion 5a of the liner 5 as shown in Figure 15B. The protrusion pattern 8 may comprise, for instance, a plurality of stripes as shown in Figure 9A or a plurality of zigzag protrusions intersecting each other as shown in Figure 9B. In the magnetic disc cartridge manufactured by the method of this embodiment, since the outer peripheral edge portion 5a of the liner 5 is more distant from the recording medium 4 than the other part, the outer peripheral edge portion Sa from which fibers are apt to be separated is less apt to be brought into contact with the rotating recording medium 4, whereby fraying of the liner 5 is suppresses and separation of fibers is suppressed. Further by virtue of the fixing agent S, liner dust or the like on the surface of the liner can be prevented from leaving the outer peripheral edge portion 5a of the liner 5.

Claims: A method of manufacturing a magnetic disc cartridge comprising a casing formed of upper and lower shell halves (1, 2) mated together, a disc-like recording medium (4) supported for rotation in the casing and a liner (5, 6) fixed to each of the inner surfaces of the upper and lower shell halves (1, 2), characterized in that the surface of an edge portion (5a) of the liner (5) facing the recording medium is made more distant from the recording medium than the other part of the liner (5) and fixing agent (5) is caused to soak into the edge portion and is solidified there. A method as defined in Claim 1 in which the surface of an edge portion (5a) of the liner (5) facing the recording medium is made more distant from the recording medium than the other part of the liner (5) by forming a recess (1e) in the inner surface of the shell half (1). A method as defined in Claim 1 in which the fixing agent (5) is adhesive. A method as defined in Claim 1 in which the fixing agent is molten resin obtained by fusing a part of the shell half (1).

Inventors: MIZUTA AKIRA, MIZUTA, AKIRA, MIZUTA, Akira c/o Fuji Photo Film Co. Ltd.
Applicants: FUJI PHOTO FILM CO LTD, FUJI PHOTO FILM CO., LTD.
Application year: 1999
Main classification: G11B23
IPC codes: G11B23