Magnetic head supporting mechanism of double side type flexible disc drive apparatus

A magnetic head supporting mechanism equipped with a magnetic head positioning carriage of a interchangeable double side type flexible disc drive apparatus comprising a carriage having a pair of arms which is rotated in detachable to a double side type flexible disc and arms, and arm parts in the arms and sliding type magnetic heads which are respectively mounted on the arm part and slide on the surface of the flexible disc and gimbal spring placed between each sliding type magnetic head and each arm part.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an improvement of a magnetic head 
supporting mechanism in a interchangeable double side type flexible disc 
drive apparatus. 
2. Description of the Prior Arts 
It has been required to increase the capacity of memory and to reduce 
memory cost, and the demands made on memories have been remarkably 
increased. A flexible disc drive apparatus which is mainly used in a 
compact computer is a single side recording apparatus as well known. 
In the past, only a single side of the flexible medium held in a flexible 
disc cartridge used as a memory medium has been used as a magnetic 
recording memory. In view of the requirement of improving cost 
performance, a double side type flexible disc cartridge using both 
surfaces of the medium as the memory surfaces and a double side type 
flexible disc drive apparatus has been commercialized. In the single side 
flexible disc cartridge, the medium is pushed from the back surface in 
contact with one magnetic head mounted on a carriage provided for moving 
and determining the position of the magnetic head in the radial direction, 
and the head is slided on the medium to perform write-in or read-out, and 
accordingly, the mechanism is relatively simple and quality control for 
the signals is easy. 
In such an apparatus, the back surface of the medium is pushed by a pad 
made of a soft material to make contact between the medium and the head. 
On the other hand, in the double side type apparatus, the magnetic head is 
brought into contact with both surfaces of the flexible medium and 
accordingly, there are various manufacturing problems related to the 
stability of quality of signals and medium wear, in comparison with the 
single side apparatus. 
In the single side apparatus, no medium wear is observed except in case of 
rough head surface, because the head surface is spherical and pressured by 
a soft pad from the back side. 
However, in the double side apparatus, a pad can not be used, since the 
magnetic heads should be located on both surfaces of the medium. 
Accordingly, a wearing loss of the medium is produced by the magnetic 
heads on both sides of the medium. As the most severe problem, it is hard 
to prevent instant shock at the time of contacting of the medium by the 
magnetic heads. In order to prolong the life of the medium it has been 
considered to employ a method of maintaining a non-contacting condition 
during positioning of the magnetic head to a predetermined track or during 
non-operation of the apparatus, and contacting the medium at the time just 
before starting the read-out or the write-in. However, a peeling 
phenomenon is easily caused in the medium by repeating such contacts. In 
order to prevent such trouble, it is necessary to consider severe quality 
controls for the roundness value R of edges of the magnetic heads and a 
roughness of the surface of the magnetic head, a control of the contacting 
speed of the magnetic heads to the medium and a control of the angles of 
the magnetic head surfaces to the medium at the moment of contact. The 
double side type head supporting mechanism is one piece formed of a 
combination of a pressure arm and a cantilever spring supporting arm 
whereby the pressure force should be minimized in view of the life of the 
medium. Accordingly, remarkably soft structure is required to reduce the 
pressure force whereby the manufacturing process is quite difficult and 
the quality of signals is unstable. 
The present status of the conventional double side type apparatus will be 
further described. 
In FIGS. 1 and 2, the reference numeral (1) designates a spindle for giving 
a predetermined rotation to a magnetic memory medium in a flexible disc 
cartridge (2); (3) designates a cone on the spindle (1) which is fitted to 
a round hole (4) formed at the center of the medium (2); (5) designates a 
spindle cup for fitting the medium (2) to the spindle (1) by pushing the 
medium (2) from the upper position to the arrow direction A. The mechanism 
for supporting and rotating the spindle cup (5) is not shown since it is 
not important. The reference numeral (6) designates a body base for 
fitting and fixing the spindle (1). The magnetic memory medium (2) is 
rotated since the spindle (1) is rotated by a belt (not shown) on a pulley 
(30) formed in one piece with one end of the cone (3) and the belt is 
driven by a motor (not shown). A carriage body (7) is driven to change its 
position at the radial direction of the magnetic memory medium (2) by a 
lead screw or a belt, etc. (not shown). The driving source can be a known 
stepping motor (not shown). The stepping motor is firmly fixed on the body 
base (6) by L-shape fittings (not shown). An upper arm (8) is fixed on the 
carriage body (7) through a plate spring (9) with a screw (10). A lower 
arm (11) is fixed in the same manner. The plate spring (9) is formed in 
one piece by a mold inserting in an injection molding process with the 
upper arm (8) or the lower arm (11) as shown in the drawing. The reference 
numeral (28) designates each end of the upper or lower arm (8), (11); (29) 
designates an arm receiving surface formed on the carriage body. A 
projection (23) formed on each of the arms (8), (11) assists to suspend 
the support arm (14) to detach it from the surface of the magnetic memory 
medium (2). Each magnetic head assembly (12), (13) is firmly respectively 
fixed on the upper arm (8) and the lower arm (11) with each screw (25). 
The reference numeral (14) designates a head support arm attached by each 
screw (25). The reference numeral (20) designates a mounting base, which 
can be formed in one piece with arm (14) by a spot welding. A sliding type 
magnetic head (15) is firmly bonded on the end of the arm (14) with 
adhesive, etc. The reference numeral (21) designates a printed wiring 
flexible cable connected to the coil wound on the head (15) to lead out 
signals therefrom. 
Referring to FIGS. 3, 4 and 5, the functions of the conventional magnetic 
head assemblies (12), (13) will be further illustrated. 
The basic condition for using the magnetic memory medium (2) for a desired 
sliding life is to minimize the pressure force of the head (15) in an 
allowable range for maintaining signal output amplitude on the whole track 
without causing an amplitude modulation. In order to maintain a good 
following characteristic in its sliding operation to the flutter of the 
magnetic memory medium (2), a spring metal plate having a fine thin 
thickness is used as the support arm (14). Moreover, a pressure arm (16), 
is welded to the support arm (14) by a spot welding, to apply the pressure 
force on to the head (15). The end (17) of the pressure arm (16) is formed 
to push the projection (18) formed on the support arm (14). 
The magnetic head assemblies (12), (13) are mechanically highly biased to 
the medium side when in a standby status by the pushing force applied to 
the projection (18) of the pressure spring (16), as in FIG. 5. In such 
structure, it is difficult to give an ideal design wherein the end (17) of 
the spring (16) is correctly located at the top of the projection (18) in 
its operation. The stress in a rolled flat plate is not uniform, the 
stress is released at the time of cutting whereby the support arm (14) cut 
from a flat thin plate can not be kept completely. Moreover, the flatness 
of the support arm is adversely effected by the heat given by the spot 
welding of the support arm (14) on the base (20). When these causes are 
piled up, the sliding surfaces of the heads (15) mounted in the carriage 
cannot be kept in parallel with the medium (2) in operation. The deviation 
of flatness of the support arm (14) causes also a deviation of line of 
force from being perpendicular to the surace of the medium (2) passing 
through a top of the projection for load (18) whereby the pressure force 
slanted with respect to the surface of the head (15) is imparted and 
accordingly, a slant gap is formed between the medium and the head to 
cause reproducing loss. Because of the deterioration of the flatness of 
the support arm (14) and the slant pressure force due to its uncertain 
dimension by its complex shape, the pressure spring (16) causes quick 
motion which deteriorates its output amplitude modulation excessively by 
the rotation of the medium (2). Moreover, as the magnetic head assemblies 
(12), (13) having such problems are located facing each other, combined 
adverse effects result whereby it is not easy to adjust them. 
The undesirable amplitude modulation has been illustrated. As well known, 
such disc memory system has an important merit for interchangeability of 
the medium (2) so that the disc memory system has flourished. Thus, the 
conventional magnetic head assemblies (12), (13) have the disadvantage, 
that is, it is difficult to keep the positions of the magnetic heads (15), 
(15) for the magnetic gap within an allowable tolerance in their assembly 
because of the tendency for the support arms (14), (14) not to be flat and 
because of the cantilever structure of the support arms (14), (14). Thus, 
when they are mounted in the assembly, it is necessary to adjust the upper 
arm (8) and the lower arm (11) to the radial direction referring to the 
recorded standard medium in its operating test. Therefore, this further 
causes an output instability. Once the coincidence with line of force for 
the upper and lower magnetic head assemblies (12), (13) is found to 
provide stable amplitude, however the coincidence region is shifted by the 
adjustment of the magnetic gap position so that the undesirable condition 
is given. 
On the other hand, the magnetic heads (15), (15) are departed from the 
surface of the medium while waiting so as to prolong the life of the 
medium in operation, as mentioned. At the moment for touching again the 
two facing magnetic heads come into collison with each other at each edge 
(19) of the magnetic head (15), through the medium (2) in the step of 
contacting operation. In order to improve the following characteristics of 
the magnetic head (15) to the radial direction and the circumferential 
direction, a fine thin plate is used as the support arm whereby it can not 
be balanced to the pressure spring (16), and the support arm (14) is 
bended as mentioned. Therefore, when the upper arm (8) and the lower arm 
(11) are turned to depart from the surface of the medium (2) around the 
fastening edges (26), (26) of the plate springs (9), (9) in the practical 
operation, the facing angles between the sliding surfaces of the magnetic 
heads (15), (15) and the surfaces of the medium (2) are held slanted with 
respect to each other and hard impacts are applied to both surfaces of the 
medium (2) upon subsequent touching by the edges (19), and accordingly, 
the damage is produced in an earlier period, to cause low industrial 
value. In order to overcome the disadvantage, the edges (19) should be 
formed to have the desired roundness R and is processed to form mirror 
surface. However, a hard brittle material is used as the slider, many 
processing steps are required and the processability is remarkably 
inferior for the control of the size of the predetermined R. Moreover, the 
facing angle between them is not uniform because of non-uniformity of the 
support arm (14) and the pressure spring (16) in their manufacture. 
Therefore, the value R for allowing such non-uniformity is large, and the 
flat area of the magnetic head slider (15) required for the stable sliding 
is reduced disadvantageously. The parallel condition of the surface of the 
magnetic head (15) and the surface of the medium (2) at the 
circumferential direction is often deviated in the rotation of the medium 
(2) by not only shape of the edge (19) but also distortion of the support 
arm (14), and the stick motion is caused by the contact of the forward 
edge of the magnetic head (15) in operation, so that the peeling of the 
magnetic coated membrane is disadvantageously caused in an earlier stage. 
Moreover, the rigidity of the flat cable (21) is comparable to the 
rigidity of the arm part (22), (22) of the support arm (14) whereby the 
following is also obstructed. 
The disadvantages of the conventional head assemblies of double side type 
flexible magnetic disc drive apparatus have been discussed. 
The supporting mechanism of the present invention will be illustrated 
hereunder. The features of the present invention are depending upon the 
following characteristics of the known plane gimbal spring which has round 
symmetrical shape with two-way compliance, the desired rigidity in the 
plane direction and the additional functions required for the sliding type 
disc memory. 
The modified two-way plane springs having such gimbal function have been 
used as the supporting mechanisms for the floating type magnetic heads. 
However, as described above, they have been the floating type apparatus 
whereby the rigidity in the plane two-way has not been important because 
of a small coefficient of friction of air. 
In accordance with the present invention, the gimbal spring is used in the 
contact type apparatus thereby requiring rigidity for withstanding the 
friction caused by the medium (2) and the vibration of the magnetic head 
(15) caused by the vertical flutter of the flexible medium which causes 
the running of the magnetic head on the slant surface of the medium and 
the rigidity for holding precisely the magnetic head position on the data 
track during operation. 
At the same time, a quick following response of the magnetic heads to the 
vertical flutter of the medium (2) in its rotation is required. 
The sliding type apparatus should be carefully designed in view of the 
above-mentioned functions which are not required for the floating type 
apparatus. 
In the apparatus of the present invention, various functions are improved 
over the conventional double side type apparatus already mentioned. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a magnetic head 
supporting mechanism having a signal gimbal spring for supporting a 
sliding type magnetic head which has a simple structure and can be easily 
prepared and is suitable for a double side type flexible disc drive 
apparatus. 
It is another object of the present invention to provide a magnetic head 
supporting mechanism which reduces flutter of a double side type flexible 
disc caused in its rotation by holding the disc under pressure by a pair 
of holders. 
The foregoing and other objects have been attained by providing a magnetic 
head supporting mechanism fitted to a magnetic head positioning carriage 
of an interchangeable double side type flexible magnetic disc drive 
apparatus, wherein the carriage comprises first and second arms and first 
and second magnetic head assemblies; and at least one of the first and 
second arms is rotatable to depart from or contact the double side 
flexible disc; and each magnetic head assembly is mounted on the first or 
second arm having at least one of the sliding type magnetic head for slide 
contact with the surface of the flexible disc; and each of the first and 
second magnetic head assemblies comprises a holder mounted on the first 
and second arm and a gimbal spring formed between the holder and the 
sliding magnetic head.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings, one embodiment of the present invention will be 
illustrated. 
The structure of the embodiment is substantially the same as that of FIG. 1 
except the following feature. 
In FIGS. 6 and 7, the reference numerals (108), (111) respectively 
designate upper and lower arms having the same shape as those of the 
conventional ones except eliminating the projections (23), (23) of the 
arms (8), (11) for hanging and detaching the support arm (14) from the 
medium (2). 
In the conventional apparatus, the projections are formed in order to 
shorten a time applying a large force of the pressure spring (16) to the 
medium (2) in the step of detaching or touching. However, in the present 
invention, the pressure force is applied for the head slider (15) from the 
upper arm (108) or the lower arm (111) by a round symmetrical shaped cross 
fulcrum gimbal spring (144) instead of a pressure spring (16) whereby the 
deviation of facing angles seen in the conventional apparatus is not 
notable and the projections are needless. A branched holder (120) is used 
for mounting the gimbal spring (144) and has a branched end (122), (122) 
as a fork as shown in the drawing. The gimbal spring (144) is bonded or 
welded by a spot welding at the end of the holder in one piece. A magnetic 
head (15) is firmly bonded on a central circular part (124) of the gimbal 
spring (144) with adhesive, etc. A desired hole for fitting an assembled 
magnetic head (15) can be formed at the center of the circular part (124). 
The normal method of fitting the head (15) on the gimbal spring, is a 
method of fitting the ring type head core itself into its hole to use the 
core surface at the side of the magnetic gap as a floating surface; or a 
method of fitting the head core into a shoe and mounting a female screw 
nut in the shoe and fitting it to the gimbal spring with a small bolt. In 
the former method, the bonding force between the core and the spring is 
depending upon the side surface of the hole of the spring as its center 
and accordingly, it has poor reliability. On the other hand, in the latter 
method, the reliability on its strength is high, but it is disadvantageous 
in view of the manufacturing cost. 
A corner part (127) is formed in the side of the holder (120) at the side 
fixed with the upper or lower arms (108), (111) whereby the flat cable 
(21) etc. can be held smoothly. This is considered to prevent the rigidity 
of the cable (21) from adversely effecting the gimbal spring (144). 
The functional advantage of the structure is as follows. When the upper arm 
(108) and the lower arm (111) are turned to the sides of the medium (2), 
each around the edge of the plate spring (109) fastened to the carriage 
(7), the head assembly (120) supported on the arms (108), (111) approaches 
the medium (2). In the step of approaching the edges (128) of the arms 
(108), (111) to the arm receiving surface (29) of the carriage (7), the 
magnetic head (15) supported on the gimbal spring (144) is brought into 
contact with the medium and it begins to be bent by the contact pressure 
thereby the contact force builds up from a minimal value. Moreover, the 
angle between the head surface (15) and the medium (2) is small because of 
no deviation force caused by the pressure spring (16) to the support arm 
(14) as in the conventional apparatus, and the roundness R value of the 
head (15) can be remarkably reduced. 
The gimbal spring (144) which can be compact in comparison with the support 
arm (14) in the conventional apparatus, has less strength caused by 
releasing stress caused by cutting. Thus, the parallelism of the head (15) 
with the circumferential direction of the medium (2) in its rotation can 
be easily maintained. As well as the stick motion can be remarkably 
reduced and the pressure can be uniformly applied to the surface of the 
head (15) as the pressure force can be held perpendicular at the center of 
the head (15). Accordingly, there is no instability factor for the signal 
amplitude modulation which is caused in the conventional apparatus. In 
comparison with the conventional apparatus, the instant shock at the 
touching is weakened to reduce remarkably the wear of the medium (2). 
As well as the improvement of the function, the accuracy of parts in the 
preparation can be maintained because of its simple structure. In the 
conventional magnetic head assembly (12), (13), the required accuracy in 
its assembly is not easy to realize even though a special tool is used 
thereby causing a trouble in its preparation. In accordance with the 
system of the present invention, it is quite simple. The unstable support 
arm (14) in its longitudinal direction in the conventional apparatus is 
replaced by the holder (120) having high rigidity. This advantage is 
attributed to this invention. 
The second embodiment of the present invention which has a pushing function 
for controlling the opening windows of a disc jacket so as to improve the 
characteristics of the gimbal spring of the first embodiment will be 
illustrated. 
Referring to FIGS. 8 and 9, the head assembly in the second embodiment of 
the present invention will be illustrated. 
The head (201) is the same as the conventional slide type magnetic head and 
the support arm (14) used in the conventional apparatus is replaced by the 
known symmetrical round gimbal spring (202) adopted for the present 
invention. The magnetic head (201) is mounted at the center of the gimbal 
spring (202). A hole (203) is used for inserting the head core (204) and 
bonding it to the spring (202). The reference numeral (205), (205) 
designates arms of a branched holder (213) on which the flat surfaces 
(215), (215) are formed in lower step from the surface (216) of the holder 
(213) at the medium side. The fitting edges (214), (214) of the gimbal 
spring are bonded to the flat surfaces (215), (215) by spot welding or 
adhesive. Thus, the predetermined distance is given between the surface 
(216) and the slide surface (217) of the magnetic head (201). 
Referring to FIG. 10, the operation of the apparatus of the second 
embodiment of the present invention will be further illustrated. 
In FIG. 10, the opening windows (218), (218) of the jacket (220) for the 
double side type magnetic recording medium (219) are formed and the 
magnetic heads (201), (201) are brought into contact with the recording 
medium through the windows under pressure to write in or to read out 
signal data. The recording medium (219) is flexible and is locally 
undulated as a characteristic of a plastic sheet whereby it is difficult 
to use in bare style. The recording medium is usually held in a jacket 
having flexibility to ensure easy handling, protection from damage and to 
control the undulation of the medium called as the Flexible Disk Cartridge 
or commercially Diskette. The jacket edges at the opening (218), (218) are 
easy to separate from the medium (219), whereby a thickness of the 
cartridge is varied. This causes a larger flutter of the recording medium 
(219) passing below the opening windows (218), (218). The flutter at the 
part causes troublesome output amplitude modulation. 
In the second embodiment, the surface (216) of the holder (213) is located 
so as to push on the jacket (220) softly from its upper and lower side of 
the jacket around the windows as shown in the drawing. This is an 
additional mean besides the platen and bail nearer to the windows. 
Accordingly, the flutter of the recording medium (219) in the jacket (220) 
is reduced. The soft pushing of the jacket around the opening windows 
(218), (218) by the holders (213), (213) is designed also to prevent 
troublesome interference of the jacket (220) with the gimbal spring (202). 
On the other hand, all improvements are kept in the same manner as 
illustrated in the first embodiment of the invention. The unstable 
function of directivity of the pressure force to the recording medium 
which is a problem in the conventional magnetic head supporting mechanism 
having the frame type support arm (14) can be eliminated by replacing the 
pressure spring (16) by the gimbal spring (202) which easily coincides 
with the supporting point of the pitching and rolling motions to the 
center of the magnetic head (201). 
In the conventional apparatus, the support arm (14) has uncertain length 
with flexibility and distortion, so that the reliability for track 
positioning is poor. However, both edges (214), (214) of the gimbal spring 
(202) used in the present invention are firmly mounted on the holder (213) 
whereby the rigidity is high enough and the reliability of the positioning 
is remarkably high. The control of the pressure force can be excellent 
since it depends upon only the variation of the thickness of the gimbal 
spring (202). 
In this embodiment, the surface (216) of the holder (213) directly pushes 
the jacket (220). However, it is possible to modify it to an embodiment 
involving projecting a part of the rotary arm (222) fitting the holder 
(213) or an embodiment involving bonding felt or sponge rubber sheet on 
the surface (216) of the holder (213). 
From the viewpoint of protecting the interference of the jacket (220) with 
the gimbal spring (202), it is sufficient to form the stepping surfaces 
(215), (215) sink from the surface of the holder (216) without pushing the 
jacket by the surface of the holder (213). Thus a purpose of the invention 
can be satisfied. 
Referring to FIG. 10, the apparatus having the supporting mechanism of the 
present invention will be further illustrated. The magnetic recording 
medium (219) is fitted to the rotary spindle fixed to the body base (223) 
with a fastening bolt (not shown) and it is rotated. The spindle (224) is 
rotated through a belt (not shown) driven by a motor (not shown). The body 
base (223) usually has a box shape. In the drawing, only the bottom is 
shown. A carriage (225) is driven in the drawing, only the bottom is 
shown. The carriage (225) is driven linearly by the rotation of male screw 
driven by a stepping motor (not shown) wherein the male screw (not shown) 
is fitted to a female screw (not shown) formed on the carriage (225), or 
driving by belt from the pulley coupled to a stepping motor (not shown). 
The stepping motor is firmly mounted on one surface of the box type body 
base (223). The carriage (225) is supported by a guide shaft (not shown) 
for the linear guide. The guide shaft is suspended on two poles (not 
shown) standing on the bottom of the body base (223). The linear 
reciprocal movement of the carriage (225) to the rotary center of the 
recording medium (219) can be performed by sliding on the guide shaft 
fitted to the guide hole (not shown) of the carriage (225). A guide slot 
(226) for the disc cartridge is located on the carriage, and each 
receiving part (228) is formed on the carriage at the end of the rotary 
arm (222) at both upper and lower parts. A plate spring (227) is mounted 
on the other end of the rotary arm (222). The other end of the plate 
spring (227) is firmly fitted to the carriage (225) with a screw (229). A 
pedal (230) is formed in one piece at the bottom of the rotary arm (222). 
The upper and lower rotary arms are assembled to make contact of both 
pedals (230), (230). A lift arm (231) is formed in one piece on one side 
surface of the end of the upper rotary arm (222). The arm (231) is pulled 
up by a magnet (not shown) mounted on the body base (223) to the arrow 
direction B. When the magnet is stopped energizing, it is returned to the 
condition of FIG. 10 by the force of the plate spring (227). 
The lower rotary arm (222) is turned by pushing the pedal (230) of the 
lower rotary arm (222) by the movement of the upper rotary arm (222). 
The operation of the magnetic head supporting mechanism equipped with the 
rotary arms (222), (222) which drive as mentioned above, has been 
illustrated. 
The supporting mechanism of the present invention is different from the 
conventional supporting mechanism. In the latter, the head edge (232) is 
firstly landed on the recording medium whereas in the former, the head 
edge (233) is firstly landed on the recording medium. In the former, the 
inner deviation i.e. the pushing force is initially applied to the medium 
(219) and the angle of the sliding surface of the head (201) to the 
surface of the medium (219) is larger depending upon the deviation of 
force whereby the medium is notable. In the former, the edge (233) is 
brought into contact with the surface of the medium (219) and the pressure 
force is gradually increased and the angle is remarkably small whereby the 
medium wear can be remarkably small. 
Referring to FIGS. 11 to 17, a sliding magnetic head supporting mechanism 
having an excellent medium following function will be illustrated as a 
third embodiment of the invention. 
In the third embodiment of the present invention, the magnetic head 
assembly (350) shown in FIG. 11 similar to the magnetic head assembly 
(112) of FIG. 6 and the magnetic head assembly (351) shown in FIG. 13 
which has different structure from the magnetic head assembly (350), are 
combined. 
In FIGS. 11 and 12, the magnetic head assembly (350) comprises the sliding 
type magnetic head (301), the gimbal spring (302), the rectangular hole 
(303), the head core (304), the branch arm part (305), the branched holder 
(309), the sliding surface (310), the fitting hole (311), the fitting edge 
(312), the fitting screw (317), the upper rotary arm (318) and a plate 
spring (325) as those of FIGS. 6 and 7. 
Referring to FIGS. 13 and 14, the other magnetic head assembly (351) will 
be illustrated. 
The known gimbal spring (302) i.e. a symmetrical round shaped two way 
flexible cross fulcrum plate spring is used in the embodiment. The gimbal 
spring (302) is used instead of the support arm (14) having a long 
rectangular shape of FIG. 3. The gimbal spring (302) shown in FIG. 11 has, 
at the central part, a rectangular hole (303) in which the head core (304) 
is inserted and bonded at the predetermined position. The branch arm part 
(305) of the holder (309) is provided for bonding the fitting edges (312), 
(312) of the gimbal spring (302) on the branched holder (309) by spot 
welding or adhesion. The part having the function of the present 
embodiment is assembled at the back side of the fitting surface (305) of 
the gimbal spring (302); that is the other gimbal spring (313) having the 
same shape for its spring functional part and its fitting edges as those 
of the gimbal spring (302), however, a load arm (307) is formed in one 
piece instead of the head (301). A predetermined space is kept between the 
edge (308) of the load arm (307) and the top of a projection (306) formed 
on the gimbal spring (302) as shown in FIG. 16. The projection (306) is 
the same as the projection (18) formed at the support arm (14) as the 
known rectangular frame type plate spring. The top of the projection also 
corresponds to the center in its plane view of the magnetic head (301). 
The gimbal spring (313) is mounted on the back surface (314) of the 
branched ends (305), (305) of the holder (309) by a spot welding, etc. by 
the same manner to correspond its center to the center of the gimbal 
spring (302) in plane view. 
In this embodiment, a gap is formed between the load arm (307) and the 
projection (306). However, it is possible to arrange them to be brought 
into contact with each other under non-load condition. 
The main structure of the improved embodiment has been described. The 
present embodiment of the magnetic head supporting mechanism and its 
operation will be described in detail. 
FIG. 17 shows the supporting mechanism for supporting the head (301) 
through the gimbal spring (302) on the holder (309). The magnetic head 
assembly (350) shown in FIG. 11 is firmly fixed on the upper rotary arm 
(318) with the screw (317) so as to locate the head on the upper surface 
of the disc (316) in the disc cartridge (315). The magnetic head assembly 
(351) shown in FIG. 13 is firmly fixed on the lower rotary arm (319) with 
the screw (317) to locate on the lower surface of the disc (316). The 
magnetic head assembly (350), (351) are fixed on rotary arms (318), (319) 
and they are fixed with a screw bolt (340) at the rear part of the plate 
spring (325). 
The flexible disc (316) is fitted on the rotary spindle (324) fixed on the 
body base (320) with the fastening bolt (not shown) to be rotated. The 
spindle (324) is rotated by the belt (not shown) driven by the motor (not 
shown). The structure of the body base (320) is not shown, but it is 
usually a box shape. Only a part of the bottom of the body base is shown. 
The carriage (321) is used for the linear movement for positioning to the 
desired track on the disc (316) to read or write. The linear movement is 
generated, for example, on a female screw on the carriage by rotating the 
male screw (not shown) driven by the stepping motor (not shown). 
The rotation of the carriage (321) by the screw is stopped and only linear 
movement is given by forming a U-shape guide or a round hole on the 
carriage (321) fitting to the guide shaft (not shown). The shaft is held 
in suspended form on the body base (320). This is not shown in the 
drawing. 
A guide slot (322) for the disc cartridge (315) is formed on the carriage, 
and each receiving part (323) is formed at each end of the upper and lower 
rotary arms (318), (319). Each plate spring (325) is mounted in one body 
at the other end of the rotary arm (318) or (319). The other free end of 
the plate spring (325) is firmly fixed on the rear part of the carriage 
(321) with a screw bolt (340). Each pedal (326) is formed in one piece on 
each rotary arm (318), (319) at its rear bottom and the rotary arms are 
combined to be brought in to contact each other A lift arm (327) is formed 
in one piece near the front end of the upper rotary arm (318). The arm 
(327) is pulled up to the arrow direction C by the magnet (not shown) 
mounted on the body base (320). When the magnet is stopped energizing, the 
arm is returned to the condition shown in the drawing by the function of 
the plate spring (325) and the auxiliary spring (228). Accordingly, the 
magnetic head (301) can be brought into contact with the disc (316). 
The characteristic function of the third embodiment in the operation to the 
final contact will be further illustrated. 
When the magnet is stopped energizing, the upper rotary arm (318) is 
falling to approach the disc surface (316). The upper and lower rotary 
arms (318), (319) are moved to promote the approach of the magnetic heads 
(301), (301) to respective surfaces of the disc (316) as shown in the 
drawing upon cessation of the pushing force applied to the lower pedal 
part (326) pushed by the upper pedal part (326). 
When the sliding surface (310) of the magnetic head (301) on the lower 
rotary arm (319) begins to make contact with the surface of the disc 
(316), the bending operation of the gimbal spring (302) is started. When 
the bending degree increases, the top of the projection (306) on the 
magnetic head (301) is brought into contact with the end (308) of the load 
arm (307). After that time the pressure force increases rapidly given by 
the two gimbal springs (302), (313), to form a bending point of the 
load-bending curve. 
During further falling of the rotary arm (319) to the medium (316) to reach 
the end (323) of the carriage (321), the magnetic head (301) gradually 
come close to the arm (319) to store the strain energy being equal to the 
pressure force supported by the gimbal springs (302), (313). 
On the other hand, the upper rotary arm (318) hold only one gimbal spring 
(302), and accordingly, the load-bending curve is substantially linear 
until the finish of the operation. At the finish of the operation, that 
is, the stationary condition of the rotary arms (318), (319), the magnetic 
heads (301), (301) are pressed against each other by the spring forces of 
the gimbal springs (302), (302) and (313) to be balanced in the principle 
of action and reaction. 
When the disc (316) is rotated at the balanced condition, the surface is 
vertically vibrated by its own undulation and dynamic flutter of the 
medium (316), however, the projection (306) of the lower magnetic head 
(301) is brought into contact with the load arm (307) on the gimbal (313) 
and the gimbal spring (313) is vertically moved to follow the movement of 
the disc (316), whereby the gimbal spring (302) equipped with the magnetic 
head (301) is moved around the contact as the rotary center of the rolling 
and pitching. 
On the other hand, the upper magnetic head (301) is in a condition of 
sliding in contact with the upper surface of the disc (316) and does not 
have a rotary center for the rolling and pitching in it as that of the 
lower magnetic head (301). However, the moment of the following movement 
of the lower magnetic head (301) is transferred through the disc (316) and 
the upper magnetic head also follows the surface of the disc (316) in 
conjunction with the upper gimbal spring (302). Accordingly, a pseudo 
rotary center is given for the upper magnetic head (301) by the projection 
(306) and the gimbal spring (313) etc. 
As described in detail, in the magnetic head supporting mechanism of the 
third embodiment of the present invention, the undesired operation caused 
by the conventional supporting mechanism of FIGS. 1 to 4 having the upper 
and lower projections can be prevented. The rotary center is given in 
comparison with the first embodiment whereby a highly sensitive following 
characteristic even for a small moment, is given. 
The second gimbal spring (313) and the load arm (307) are shown, however, a 
projection (306) can be formed on a cantilever spring instead of this 
gimbal spring (313), as the other embodiment of the present invention. In 
order to maintain a good following characteristic for a vertical movement 
of the disc (316), it is very suitable to form a pair of cantilever 
springs in parallel, with a projection in one piece. The second gimbal 
spring (313) can be added to the upper arm (318) in the reversed manner as 
the above illustration. The gimbal springs are illustrated as a round 
type, but it can be designed to be a symmetrical rectangular shaped cross 
fulcrum type. These modifications can be understood from the above 
description.