MAGNETIC DISC DEVICE

Abstract: A half-height magnetic disc device comprising: a base (1); four magnetic discs (4) arranged one above the other on the base (1); five head arms (6e) rotatable about a pivot (6f) for seeking motion on both surfaces of each magnetic disc (4); eight magnetic heads (5) each attached to an end of the head arm (6e) through springs (8, 9) facing a surface of each disc (4); a rotational drive unit (6b, 6c) for swinging the head arms (6e); a main printed circuit board (7) arranged on a rear side of the base (1); and, a cover (2) which covers an upper surface of the base (1).

Description: The present invention relates to a magnetic disc device used as a memory for, for example, a mini-computer or a micro-computer. Conventionally, a Winchester type magnetic disc device using hard discs 3.5 inch (89 mm) in diameter has been used as a memory means for, for example, a mini-computer or a micro-computer. Such a magnetic disc device should, if possible, have a high memory density without any enlargement of its size, to ensure that it is compatible with other conventional devices. A conventional magnetic device typically comprises a record medium on which information data is recorded and a magnetic head for reading the information from that medium. The magnetic head is disposed in such a manner that it faces the recording area of the record medium, to transmit information data between the record medium and a read/write device. When a magnetic disc is used as the magnetic medium, the head is attached to a head arm which carries the head and positions it at a desired track in the recording area of the magnetic disc. Therefore, to achieve an accurate positioning of the head at a high speed, it is necessary to reduce the weight of the head construction, including the head arm, to minimise its inertia. The height dimension of a magnetic disc device is commercially standardised and a full-height magnetic disc device is marketed. Such a full height magnetic disc device is described in the European application EP-A-0157017 and comprises a case having a base, a number of magnetic discs, a number of magnetic heads, a head actuator and a motor for driving a spindle of the magnetic discs. The head actuator comprises a head arm which is rotatable about a pivot, and the pivot comprises an outer sleeve mounted on a stationary shaft. The shaft is supported at both ends providing good stability but requiring additional space thus preventing any significant reduction in the height of the disc device. Also, a half-height magnetic disc device has been developed with half the memory capacity to realise a small capacity and size magnetic disc device which is compatible with the full-height magnetic disc device, and advantageous from the standpoint of space saving since the height is a half of that of the full-height magnetic disc device. Such a half-height magnetic disc device is described later with reference to Figure 5 of the drawings. When the capacity of the magnetic disc device is to be increased using an ordinary interface circuit, it is desirable to double the number of the discs it contains, from the standpoint of easy installation of a new magnetic disc device having an increased capacity in place of an old device, since it is easy to exchange an old device with a new one and/or simultaneously use a new device with an old one through an ordinary interface circuit. Therefore, a two-disc magnetic disc device was developed as an improvement on a one-disc magnetic disc device. Subsequently, a magnetic disc device comprising four discs has been developed as an improvement on the two-disc device. According to this invention a disc device comprising: a case having a base; a plurality of magnetic discs; a plurality of magnetic heads; a head actuator; a motor for driving a spindle of the magnetic discs; the magnetic discs, the magnetic heads and the head actuator being housed within the case; and the head actuator comprising a head arm which is rotatable about a pivot, and the pivot comprising an outer sleeve mounted on a stationary shaft, is characterised in that a lower inner peripheral edge of the outer sleeve is inclined, and the shaft is supported on a seat which has an inclined periphery corresponding to the inclined peripheral edge of the outer sleeve. Preferably each of the head arms includes a groove-like lead wire holding means formed along the lead wire path, the lead wire being fitted and held therein. The present invention makes it possible to house four discs in a half-height magnetic disc device. This could not be realised by the prior art device, since four discs could not be stacked in the shortened half-height device housing when the device had the prior art structure. The present invention provides a magnetic disc device which eliminates unnecessary dead space due to the pivot seat of the head actuator, thus realising a compact device. Particular embodiments of a magnetic disc device in accordance with this invention will now be described and contrasted with the prior art with reference to the accompanying drawings; in which:- Figure 1 is a plan view of a magnetic disc device according to the present invention, with the cover removed; Figure 2 is a vertical sectional view of the magnetic disc device according to the present invention; Figure 3 is a disassembled view of the magnetic disc device according to the present invention; Figure 4 is a sectional view of a pivot of the magnetic disc device according to the present invention; Figure 5 is a sectional view of a pivot of a magnetic disc device according to the prior art; Figure 6 is an explanatory view of a magnetic head arm according to the prior art; Figure 7 is an explanatory view of the head arm of the magnetic disc device according to the present invention; Figures 8(a) and 8(b) are explanatory views of another example of the head arm, wherein Figure 8(a) is a plan view and Figure 8(b) is a sectional view along the line A-A′ of Figure 8(a); and, Figures 9(a), 9(b) and 9(c) are explanatory views of still another example of head arm of the present invention, wherein Figure 9(a) is a plan view, Figure 9(b) is a sectional view along the line B-B′ of Figure 9(c) is a sectional view along the line C-C′ of Figure 9(a). A conventional magnetic disc device comprises a head actuator having a pivot 6f, as shown in Figure 5. The pivot 6f comprises a plurality of head arms 6e which are secured to an outer sleeve 10. The outer sleeve 10 is installed on a stationary shaft 12 through two roller bearings 11 and 11′. The shaft 12 is disposed on a seat 12a for vertical positioning when secured to the base 1 through a screw. The diameter of the seat 12a is approximately the same as that of the outer sleeve 10. Therefore, the space corresponding to the height H of the seat 12a is wasted, thus causing an unnecessary enlarging of the case of the magnetic disc device. Figure 3 is a disassembled perspective view of a magnetic disc device according to the present invention. The magnetic disc device comprises: a housing formed by a base 1 and a cover 2; four magnetic discs 4 secured to a spindle 3; eight magnetic heads 5 for magnetic read/write operations at the upper and lower surfaces of each magnetic disc 4; and a head actuator 6 for swinging the magnetic heads 5 in the direction of the arrow AA′ on the magnetic disc surface. The head actuator 6 comprises a drive motor 6a, a capstan 6b, a steel belt 6c, a sector 6d, head arms 6e, and a pivot 6f. Below the base 1 are disposed a spindle drive motor (not shown), a printed circuit board for driving the spindle drive motor (not shown), and a main printed circuit board 7 mounting a read/write circuit for reading data from and writing data on the magnetic disc. The magnetic head 5 is attached to the head arm 6e through a gimbal spring and a load spring 8. The magnetic disc device illustrated in Fig. 1 is seen from the upper side thereof, with the cover removed, and Fig. 2 shows a vertical section thereof. This magnetic disc device is of a half-height type having a commercially standardized outer shape dimension. That is, the disc diameter is 96 mm, the longitudinal length a = 146 ± 0.5 mm, the lateral length b = 101.6 ± 0.5 mm, and the height c = 41.3 ± 0.3 mm. A bottom plate 30 (Fig. 2) for covering the main printed circuit board 7 is disposed below the base 1 and secured thereto together with the main printed circuit board 7 by screws. The height c is the dimension between the lowest surface of the bottom plate 30 and the top surface of the cover 2. The gap d between the adjacent magnetic discs 4 is 4.5 mm, and the thickness t of each magnetic disc 4 is 1.27 mm. Five head arms 6e are arranged to conduct a seeking motion on both surfaces of the four magnetic discs 4, as shown in Fig. 2. The thickness of the two uppermost and lowermost head arms is 2.0 mm, and the thickness of the three intermediate head arms is 2.8 mm. The tip of each head arm 6e is thinned to 1.154 mm to attach the load spring 8. The gap between the lower surface of the lowermost magnetic disc 4 and the upper surface of the base 1 is 3.5 mm. Also, as described later, the gap w (Fig. 4) between the lower surface of the lowermost head arm 6e at the pivot portion and the upper surface of the base 1 is 0.5 mm. The magnetic discs 4 rotate in the direction of the arrow R (Fig. 1). A baffle plate 41 is disposed corresponding to each of the four magnetic discs 4 facing the upper surface thereof, and a filter 2 is incorporated with the baffle plates 41 to capture dust particles on the disc surface. The magnetic head 5 is connected to a flexible printed circuit broad 43 (shown by a dash-dot line) bonded behind the head arm 6e through a lead wire 5a′. A head IC (preamplifier) 44 is mounted on the flexible printed circuit board 43 behind the head arm 6e. The flexible printed circuit board 43 is connected to a connector 45 disposed at a corner of the base 1. The flexible printed circuit board 43 is loose and can be folded back and forth within the rear end of the head arm 6e to allow free movement without impeding the swing motion of the head arm 6e. The connector 45 is connected to the main printed circuit board 7 (Fig. 5) disposed under the base 1. A pivot structure of the head arm according to the present invention is illustrated in Fig. 4. In the drawing, numeral 1 designates a base; 6e designates a head arm; 10 designates an outer sleeve; 11 and 11′ designate roller bearings; and 12 designates a stationary shaft. As shown in the drawing, this embodiment of the pivot structure comprises the outer sleeve 10, which supports a plurality of head arms 6e simultaneously, and the stationary shaft 12 which rotatably supports the outer sleeve 10 thereon through two roller bearings 11 and 11′. The stationary shaft 12 is placed on a seat 12a having a diameter which is approximately the same as that of the outer sleeve 10, to ensure the verticality of the shaft which is secured to the base 1 by a screw, similar to the prior art structure of Fig. 5. A primary feature of this embodiment resides in the structure wherein the inner peripheral edge of the lower end of the outer sleeve 10 is inclined and the outer periphery of the seat 12a of the shaft 12 is also inclined in a direction facing the inner inclined lower end of the outer sleeve 10. With such a structure, the seat 12a is arranged to fit into the inclined lower inner edge of the outer sleeve 10, thus eliminating the unnecessary dead space corresponding to the height H of the seat as described with reference to Fig. 5 of the prior art structure. Therefore, it is possible to reduce the height of the magnetic disc device. As mentioned above, in accordance with the present invention, it is possible to eliminate the dead space for the pivot seat, with a very simple structure, thus realizing a small-sized magnetic disc device which is practically very useful. This is because the distance w (Fig. 4) between the lower surface of the head arm 6e and the upper surface of the base 1 is considerably reduced. A prior art magnetic head structure is illustrated in Figure 6. A head 33 is supported at an end of a gimbal 32 which is secured to a head arm 31. Information data is transmitted between the head and a read/write device through a lead wire 34. A springy clip 35 made of plastic is attached to the head arm 31 to hold the lead wire 34 between the head arm 31 and the clip 35 along the head arm side edge. With the above-mentioned magnetic head structure of the prior art, the head arm 31 becomes heavy, since the clip 35 is used for holding the lead wire 34, thus opposing the requirement for reducing the weight of the head arm structure. Also, the gap between the discs must be wide enough to dispose the clips 35 therein, which prevents a reduction of the height of the magnetic device. A coil lead wire cable arrangement according to the present invention is described hereinafter with reference to Figures 7 and 9. Figure 7 is an explanatory view of the principle of the arrangement of the present invention. In Figure 7, numeral 36 designates a cable holding means comprising a groove formed along the cable pass. The cable 34 is fitted into this groove. The cable 34 is fitted and held in the groove of the holding means 36 formed in the head arm 31. Therefore, it is unnecessary to use a special instrument for holding the cable like a clip to hold the cable, thus reducing the weight of the magnetic head structure. An example of the cable holding arrangement according to the present invention is illustrated in Figures 8(a) and 8(b), wherein the same parts as shown in Figure 7 are designated by the same numerals. Figure 8(a) is a plan view of the arrangement and Figure 8(b) is a sectional view along the line AA′ of Figure 8(a). A groove 37 is formed as a cable holding means along the cable pass on the head arm. Figure 8(b) shows a cross section of the groove 37, which comprises a rectangular recess for receiving the cable 34. The cable 34 is held in this groove 37 by press fitting the cable into the groove. An adhesive agent may be used to firmly hold the cable 34 within the groove 37. Another example of the cable holding arrangement according to the present invention is illustrated in Figure 9(a), 9(b) and 9(c). A step is formed along the cable pass on the head arm 31, as shown in Figure 9(b) which shows a cross section along the line BB′ of the head arm 31 of Figure 9(a). A plurality of holder projections 38 are disposed along the step of the cable pass to partly form a groove-like portion, as shown in Figure 9(c) which is a cross section along the line CC′ of the head arm of Figure 9(a). The cable 34 is held in this groove-like portion. As mentioned above, the magnetic head structure according to the present invention comprises a groove as a lead wire holding means formed along the cable pass on the head arm, which makes it unneccesary to use a special cable holding instrument means, thus enabling a reduction of the weight of the magnetic head.

Claims: 1.A magnetic disc device comprising: a case (1, 2) having a base (1); a plurality of magnetic discs (4); a plurality of magnetic heads (5); a head actuator (6); a motor for driving a spindle (3) of the magnetic discs (4); the magnetic discs (4), the magnetic heads (5) and the head actuator (6) being housed within the case (1, 2); and the head actuator comprising a head arm (6e) which is rotatable about a pivot (6f), and the pivot (6f) comprising an outer sleeve (10) mounted on a stationary shaft (12), characterised in that a lower inner peripheral edge of the outer sleeve is inclined, and the shaft (12) is supported on a seat (12a) which has an inclined periphery corresponding to the inclined peripheral edge of the outer sleeve (10). 2. A magnetic disc device according to Claim 1, wherein the device comprises a magnetic head structure (5) comprising a magnetic head electrically connected to a read/write means through a lead wire (5a) and a head arm (6e) supporting the magnetic head (5), wherein the head arm (6e) has a groove-like lead wire holding means (36,37,38) formed along the lead wire path, the lead wire being fitted and held therein.

Inventors: MIHARA, TAKAHISA, SAITO, SIGEO, SAMMA, SHOJI
Applicants: FUJITSU LIMITED
Application year: 1987
Main classification: G11B5
IPC codes: G11B25, G11B5, G11B33