Method of cleaning the liners of a magnetic disc cartridge.

Abstract: A method of cleaning a liner of 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 pair of liners respectively fixed to the inner surfaces of the upper and lower shell halves, which method comprising the steps of: positioning each of the shell halves bearing thereon the liner fixed thereto with the surface of the liner opposed to a front end face of an ultrasonic welding horn at a predetermined space therefrom, vibrating the liner by ultrasonic wave radiated from the front end face of the ultrasonic welding horn, and blowing an air flow against the surface of the liner.

Description: This invention relates to a method of cleaning a liner of a magnetic disc cartridge according to the pre-characterizing part of claim 1 and claim 4. 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 or 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. A method of cleaning a liner of a magnetic disc cartridge having the features of the pre-characterizing part of claim 1 and claim 4 is known from JP-A-7-272 437. In this prior art method, the shell half bearing thereon the liner is pressed against the ultrasonic welding horn. No support means are shown in the reference. The welding hom faces the side of the shell half which carries the liner. US-A-5 115 961 discloses a method of manufacturing a magnetic disc cartridge and a method of cleaning the liner of such cartridge. The cleaning is carried out immediately after the shell halves are welded. The cleaning step is carried out by blowing air over the liner with the start of an air blow, the welding horn is cut off. Summary of the Invention In view of the foregoing observations and description, the object of the present invention is to provide a method of cleaning a liner of a magnetic disc cartridge which can effectively remove dust and free fibers from the liner without damaging the casing and/or the recording medium. This is achieved by the features of each independent claim 1 and 4. Preferred embodiments are defined by the dependent claims 1. In accordance with the present invention, there is provided a method of cleaning a liner of 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 pair of liners respectively fixed to the inner surfaces of the upper and lower shell halves, which method comprising the steps of positioning each of the shell halves bearing thereon the liner fixed thereto with the surface of the liner opposed to a front end face of an ultrasonic welding horn at a predetermined space therefrom, vibrating the liner by ultrasonic wave radiated from the front end face of the ultrasonic welding horn, and blowing an air flow against the surface of the liner. It is preferred that the distance between the liner and the front end face of the ultrasonic welding horn be an integral multiple of a half wavelength of the ultrasonic wave as propagating in the air. Further the ultrasonic welding horn may be moved relatively to the liner in a range including an integral multiple of a half wavelength of the ultrasonic wave as propagating in the air. The shell half may be placed on a support table supported by an air cylinder. Brief Description of the Drawings Figure 1 is an exploded perspective view of a magnetic disc cartridge, Figure 2 is a schematic view showing a system for carrying out a method of cleaning a magnetic disc cartridge in accordance with a first embodiment of the present invention, Figure 3 is a schematic view showing a system for carrying out a method of cleaning a magnetic disc cartridge in accordance with a second embodiment of the present invention, and Figure 4 is a fragmentary view showing a modification of the system shown in Figure 22. Preferred Embodiment of the Invention In Figure 1, a magnetic disc cartridge 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 spindle 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 cleaning the liners 5 and 6 in accordance with a first embodiment of the present invention will be described with reference to Figure 2. Figure 2 shows an example of a liner cleaning system for carrying out the method of the first embodiment of the present invention. The liner cleaning system 220 shown in Figure 2 is for cleaning the liner 5 (or 6) after it is fixed to the shell half 1 (or 2) and before the shell halves 1 and 2 are assembled into a magnetic disc cartridge. The liner cleaning system 220 comprises a shell half support table 221 on which the shell half 1 with the liner 5 is placed. An ultrasonic welding horn 223 connected to an ultrasonic wave generator 222 is disposed above the shell half support table 221 with its front end face 223a directed downward. The front end face 223a of the ultrasonic welding horn 223 is opposed to the surface of the liner 5 at a predetermined distance d therefrom. An air blow nozzle 225 which blows an air flow against the surface of the liner 5 is disposed on one side of the ultrasonic welding horn 223 and a suction duct 226 which sucks dust blown away the surface of the liner 5 is disposed on the other side of the ultrasonic welding horn 223. Ultrasonic wave vibration generated by the ultrasonic wave generator 222 is applied to the liner 5 from the front end face 223a of the ultrasonic welding horn 223 and at the same time an air flow is blown against the surface of the liner 5 while the suction duct 226 sucks air. With this arrangement, fiber fractions, dust and the like trapped in the liner 5 are released from the liner 5 by vibration of the liner 5, blown away the liner 5 by the air flow and sucked into the suction duct 226, whereby the liner 5 is removed with fiber fractions, dust and the like. It is preferred that the ultrasonic wave vibration be not higher than 50kHz in frequency. More preferably the frequency is in the range of 15 to 25kHz. The distance d between the front end face 223a of the ultrasonic welding horn 223 and the liner 5 is set to an integral multiple of a half wavelength of the ultrasonic wave as propagating in the air. For example, when the frequency of the ultrasonic wave is 20kHz, the half wavelength is {340[m/s]/20[kHz]}x1/ 2=8.5mm since the speed of sound in the air at normal temperatures is about 340m/s. Accordingly, the distance d between the front end face 223a of the ultrasonic welding horn 223 and the liner 5 is preferably 8mm to 9mm. As the frequency of the ultrasonic wave becomes higher, the distance d becomes too short when it is set to a half of the wavelength. Accordingly when the frequency is 40kHz, the distance d is set to be equal to the wavelength, i.e., 8mm to 9mm. However, since as the distance d increases, attenuation becomes larger, it is preferred that the distance d be set to a half of the wavelength. The amplitude of the front end face 223a of the ultrasonic welding horn 223 should be about 1 to 40µm (half amplitude) and is preferably 10 to 20pm in the case where the frequency is 20kHz. When the amplitude is too large, the liner 5 generates heat and the shell half 1 can be damaged, e.g., deformed or fused, and at the same time, manufacture of the ultrasonic wave generator 222 and/or the ultrasonic welding horn 223 becomes difficult. The ultrasonic welding horn 223 may be moved back and forth relatively to the liner 5 in a range including an integral multiple of a half wavelength of the ultrasonic wave as propagating in the air. When the distance d is changed while the ultrasonic wave vibration is being applied to the liner 5, vibration of dust in the liner 5 is changed and cleaning action is enhanced. The amount of movement of the ultrasonic welding horn 223 is preferably 0.5 to 2mm in the case where the frequency is 20kHz. Generally, the amount of movement of the ultrasonic welding horn 223 is set larger as the frequency becomes lower. Preferably the ultrasonic wave vibration is applied to the liner 5 for 0.1 to 2 seconds. When the ultrasonic wave vibration is applied to the liner 5 for an excessively long time, the liner 5 generates heat and the shell half 1 can be damaged. Further application of ultrasonic wave of a small amplitude for a long time produced less cleaning action and a best result was obtained by application of ultrasonic wave of an amplitude of 20µm for 0.5 to 1.5 seconds. It is preferred that the air blow nozzle 225 be arranged to blow pressurized air obliquely to the liner 5 over a wide area and the suction duct 226 be arranged to suck air over a wide area. When the air blow nozzle 225 is arranged to blow ionized air, static electricity generated by the ultrasonic wave vibration can be eliminated and the cleaning action is enhanced. Further though it is preferred that the air blow nozzle 25 blows air wide over the entire area of the liner 5, it is possible to move a point type nozzle to cause air flow to scan the surface of the liner 5. Further when the air flow is turned on and off at short intervals in a pulse-like fashion, cleaning action can be enhanced. Though, in the system shown in Figure 2, the shell half 1 is directed upward with the ultrasonic welding horn 223 directed downward, it is possible to direct downward the shell half 1 with the ultrasonic welding horn 223 directed upward. In this case, dust released from the liner 5 drops away from the liner 5, which is advantageous in effectively removing the dust. After the liner is cleaned in the manner described above, the upper and lower shell halves 1 and 2 are mated together with the recording medium 4 placed therein and bonded together by ultrasonic welding, whereby a magnetic disc cartridge is assembled. A method of cleaning the liners 5 and 6 in accordance with a second embodiment of the present invention will be described with reference to Figure 3. Figure 3 shows an example of a liner cleaning system for carrying out the method of the sixth embodiment of the present invention. The liner cleaning system 320 shown in Figure 3 is for cleaning the liner 5 (or 6) after it is fixed to the shell half 1 (or 2) and before the shell halves 1 and 2 are assembled into a magnetic disc cartridge. The liner cleaning system 320 comprises a pressure receiving means 321 on which the shell half 1 with the liner 5 is placed with the liner 5 facing downward. An ultrasonic welding horn 323 connected to an ultrasonic wave generator 322 is disposed above the pressure receiving means 321 with its front end face 323a directed downward. The front end face 323a of the ultrasonic welding horn 323 is pressed against the outer surface of the shell half 1. The pressure receiving means 321 comprises a support frame 324 and an elastic means 325 for supporting the.shell half 1 in contact therewith is mounted on the support frame 324. The support frame 324 is supported on a pair of air cylinders 326. The elastic means 325 is formed of an elastic material such as rubber, resin or the like and comprises, for instance, four blocks each supporting one of the four corners of the shell half 1, thereby supporting the shell half 1 with the lower end of the outer ribs 1a spaced from the upper surface of the support frame 324. An air blow nozzle 327 which blows an air flow against the surface of the liner 5 is disposed on one side of the support frame 324 and a suction duct 328 which sucks dust blown away the surface of the liner 5 is disposed on the other side of the support frame 324. Ultrasonic wave vibration generated by the ultrasonic wave generator 322 is applied to the shell half 1 from the front end face 323a of the ultrasonic welding horn 323 and at the same time an air flow is blown against the surface of the liner 5 while the suction duct 328 sucks air. With this arrangement, fiber fractions, dust and the like trapped in the liner 5 are released from the liner 5 by vibration of the liner 5, blown away the liner 5 by the air flow and sucked into the suction duct 328, whereby the liner 5 is removed with fiber fractions, dust and the like. It is preferred that the ultrasonic wave vibration be not higher than 50kHz in frequency. More preferably the frequency is in the range of 15 to 25kHz. The amplitude of the front end face 323a of the ultrasonic welding horn 323 should be about 1 to 40µm (half amplitude) and is preferably 10 to 20µm in the case where the frequency is 20kHz. When the amplitude is too large, the shell half 1 generates heat and the shell half 1 can be damaged, e.g., deformed or fused, and at the same time, manufacture of the ultrasonic wave generator 322 and/or the ultrasonic welding horn 323 becomes difficult. Preferably the ultrasonic wave vibration is applied to the shell half 1 for 0.1 to 2 seconds. When the ultrasonic wave vibration is applied to the shell half 1 for an excessively long time, the shell half 1 generates heat and the shell half 1 can be damaged. Further application of ultrasonic wave of a small amplitude for a long time produced less cleaning action and a best result was obtained by application of ultrasonic wave of an amplitude of 20µm for 0.5 to 1.5 seconds. It is preferred that the front end face 323a of the ultrasonic welding horn 323 be pressed against the shell half 1 at a pressure of 10 to 100gf. When this pressure is excessively high, the contact surface of the shell half 1 with the ultrasonic welding horn 323 or the elastic means 325 can generate heat and can be fused and/or dust is generated. The elastic means 325 is for suppressing damage on the shell half 1 due to the ultrasonic vibration and is preferably formed of rubber, resin or the like such as those of silicone series or fluorine series which are excellent in heat resistance and durability. It is most preferred that the elastic member 325 be formed of high-expanded silicone rubber. Further since a cut surface of an expanded body is small in cross-sectional area or carrying area, it is preferred that the face of the elastic means 325 in contact with the shell half 1 is a non-cut surface (molded surface). The elastic means 325 may be formed of also a silicone rubber tube inflated at a suitable air pressure in a suitable thickness. The resilient means 325 should support the shell half 1 so that the surface of the liner 5 is kept open and an air flow between the air blow nozzle 327 and the suction duct 328 is ensured. For this purpose, it is preferred that the elastic means 325 be arranged to support the lower end face of the outer rib 1a of the shell half 1 at a plurality of points such as the four corners and/or some intermediates points or continuously along the sides other than the sides opposed to the air blow nozzle 327 and the suction duct 328. The air cylinders 326 expands and contracts according to the pressure from the front end face 323a of the ultrasonic welding horn 323 to hold constant the pressure acting on the shell half 1, thereby protecting the shell half 1 from being damaged and ensuring stable vibration of the liner 5. It is preferred that the air blow nozzle 327 be arranged to blow pressurized air to the liner 5 over a wide area and the suction duct 328 be arranged to suck air over a wide area. When the air blow nozzle 327 is arranged to blow ionized air, static electricity generated by the ultrasonic wave vibration can be eliminated and the cleaning action is enhanced. Further though it is preferred that the air blow nozzle 327 blows air wide over the entire area of the liner 5, it is possible to move a point type nozzle to cause air flow to scan the surface of the liner 5. Further when the air flow is turned on and off at short intervals in a pulse-like fashion, cleaning action can be enhanced. Though, in the system shown in Figure 3, the shell half 1 is directed downward with the ultrasonic welding horn 223 directed downward, it is possible to direct upward the shell half 1 with the ultrasonic welding horn 223 directed upward. Figure 4 shows a modification of the cleaning system shown in Figure 3. In this modification, the ultrasonic welding horn 323 is pressed against the shell half 1 only at column-like projections 232b. The projections 323b may be formed, for instance, to press the shell half 1 and apply vibration to the shell half 1 only at the four corners where the elastic means 325 supports the shell half 1. That is,.the projections 323b may be formed to press the shell half 1 in positions where the shell half 1 is less apt to be deformed by application of ultrasonic vibration, e.g., positions along the outer periphery of the shell half 1 or positions where the elastic means 325 supports the shell half 1. The position of the projections 323b may be changed according to the form of the elastic means 325.

Claims: A method of cleaning a liner of 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 pair of liners respectively fixed to the inner surfaces of the upper and lower shell halves, which method comprising the steps of vibrating the liner (5) by ultrasonic wave radiated from the front end face of an ultrasonic welding horn (223), and blowing an air flow against the surface of the liner (5), characterized by positioning each of the shell halves (1) bearing thereon the liner (5) fixed thereto with the surface of the liner opposed to a front end face of said ultrasonic welding horn (223) at a predetermined space (d) therefrom. A method of cleaning a liner as defined in Claim 1 in which the distance between the liner and the front end face of the ultrasonic welding horn (223) is an integral multiple of a half wavelength of the ultrasonic wave as propagating in the air. A method of cleaning a liner as defined in Claim 1 in which the ultrasonic welding horn (223) is moved relatively to the liner (5) a range including an integral multiple of a half wavelength of the ultrasonic wave as propagating in the air. A method of cleaning a liner of 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 pair of liners respectively fixed to the inner surface of the upper and lower shell halves, which method comprising the steps of bringing each of the shell halves (1) bearing thereon the liner (5) fixed thereto into contact with an ultrasonic welding horn (323), vibrating the liner by ultrasonic wave applied to the shell half from the ultrasonic welding horn (323), and blowing an air flow against the surface of the liner (5), characterized in that the shell half (1) is supported by an elastic means (325) disposed on the side of the shell half (1) remote from the ultrasonic welding horn (323), and the welding horn (323) is in contact with the outside surface of the shell half, i.e. the side remote from the liner. A method as defined in Claim 4 in which the shell half (1) is placed on a support table (321) supported by an air cylinder. A method as defined in claim 4, wherein the blown air is ionized.

Inventors: HAYASHI YOICHI, HAYASHI, YOICHI, Hayashi, Yoichi, 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