Magnetic tape recording and playback device with spring actuated head placement

In a magnetic tape recording and playback device, a resilient body is engaged with a head base. At the time of recording and playing back a tape, the head base is pressed and fixed when the resilient member is directly pushed by a drive plate, and at the time of withdrawing the head, the head base driven by the drive plate, through the resilient member, and the head base is pressed and fixed. In this way, a force given to the resilient body is reduced at the time of head base movement. It is possible to reduce the required head base drive force at the time of head base movement.

BACKGROUND OF THE INVENTION 
The present invention relates to a cassette type tape recorder to which a 
tape cassette accommodating a magnetic tape is applied, and more 
particularly relates to a mechanism by which a magnetic head is pulled out 
and withdrawn. 
FIGS. 11 and 12 are plan views showing a conventional magnetic tape 
recording and playback device disclosed, for example, in Japanese 
Unexamined Patent Publication No. 60-113349. FIG. 11 is a view showing the 
condition of withdrawal, and FIG. 12 is a view showing the condition of 
advance in the case where the tape is recorded and played back. 
Next, the operation will be explained as follows. 
FIGS. 11 and 12 show a mechanism for moving a magnetic head mounting plate 
102 from a withdrawal position (stopping position) to an advance position 
(acting position). A drive gear 189 is attached onto the reverse side of a 
primary base plate (not shown in the drawing) close to a gear 138. This 
drive gear 189 includes: a resting section 190 in which a portion of the 
gear is cut away; a spring receiving protruding section 191 formed on the 
upper surface side; a spiral rotary cam 192 provided on the lower surface 
side; and a stopping time engaging section 193 also provided on the lower 
surface side. A stopper wall 194 is protruded from a lower surface 
peripheral section of the drive gear 189. Further, an acting time engaging 
section 195 is protruded at a position close to the stopping time engaging 
section 193. 
In this connection, a movable iron core 110a of a magnet plunger 110 is 
pushed in the extended direction by a coil spring 110b at all times. When 
a solenoid is energized with current due to the insertion of a cassette, 
the movable iron core 110a is withdrawn into the solenoid. In the 
drawings, numeral 196 is an engagement lever, one end of which is a cam 
engaging section 196a, and the other end of which is a plunger engaging 
section 196b. The plunger engaging section 196b is engaged with a fore end 
portion of the movable iron core 110a of the magnet plunger 110, and the 
cam engaging section 196a is disposed along the lower surface of the 
rotary cam 192. In the drawings, numeral 197 is a leaf spring (a rod 
spring may be used), the free end of which comes into pressure contact 
with the spring receiving protruding section 191 so that a torque is given 
to the drive gear 189 to rotate it counterclockwise in the drawings. 
Further, in the drawing, numeral 198 is a cam lever, which is rotatably 
pivoted on the reverse side of the primary base plate. At one end of the 
cam lever 198, a cam follower 198a is provided coming into contact with 
the cam surface of the rotary cam 192. A rod spring 199, the modulus of 
elasticity of which is high, is attached to this cam lever 198, and a fore 
end portion of this rod spring 199 is engaged with a portion of the 
magnetic head mounting plate 102. In this connection, numeral 200 is a 
tension spring for returning the magnetic head mounting plate 102 from the 
acting position to the stopping position. By the resilient force of this 
tension spring 200, the cam follower 198a is pressed onto the cam surface 
of the rotary cam 192. 
Therefore, at the stopping time, as illustrated in FIG. 12, the cam 
engaging section 196a of the engaging lever 196 is engaged with the 
stopping time engaging section 193, and the resting section 190 is opposed 
to the gear 138. A resilient force of the leaf spring 197 is activated on 
the spring receiving protruding section 191, so that a torque is given to 
the drive gear 189 to rotate it counterclockwise in the drawing. The cam 
follower 198a is located at a position where the radius of the rotary cam 
192 is minimum. Consequently, the magnetic head mounting plate 102 is 
maintained at the withdrawal position (stopping position) by the action of 
the tension spring 200. 
When a tape cassette is inserted into the device under the above condition, 
the solenoid of the magnet plunger 110 is energized with current, and the 
engaging lever 196 is rotated by the operation of the movable iron core 
110a, so that the cam engaging section 196a is released from the stopping 
time engaging section 193, and the drive gear 189 is slightly rotated by 
the action of the leaf spring 197 and meshed with the gear 138. Therefore, 
the rotation of the gear 138, that is, the rotation of the motor is 
transmitted to the drive gear 189, and the drive gear 189 is rotated 
clockwise approximately by one revolution. During the rotation of the 
drive gear 189, the cam follower 198a is moved to the maximum radius 
portion of the rotational cam 192, and the cam lever 198 is greatly 
rotated, so that the magnetic head mounting plate 102 is moved to an 
advance position, resisting a force of the tension spring 200 (shown in 
FIG. 12). At this time, the cam engaging section 196a is engaged with the 
acting time engaging section 195, so that the drive gear 189 is stopped. 
However, the resting section 190 is opposed to the gear 138 again, and the 
leaf spring 197 comes into pressure contact with the spring receiving 
protruding section 191. Therefore, a torque is given to the drive gear 189 
so as to rotate it counterclockwise. The device is maintained under the 
above condition. 
In order to provide a stopping condition, an electric current supplied to 
the magnet plunger 110 may be stopped. Simultaneously when the electric 
current is stopped, the movable iron core 110a returns to the extended 
direction, and the cam engaging section 196a of the engaging lever 196 is 
released from the acting time engaging section 195. Therefore, the drive 
gear 189 is a little rotated by the action of the leaf spring 197, and the 
cam follower 198a drops to the minimum radius section of the rotary cam 
192. Accordingly, the head panel 102 is returned to the stopping position 
by the action of the return spring 200. 
In this connection, there is provided a mechanism (not shown in the present 
drawing); but illustrated in J60-113349 by which the rotary plates, are 
rotated and linked with the withdrawal motion of the magnetic head 
mounting plate 102, so that the right and left gears are separated from 
the adjacent gears. Therefore, simultaneously when the magnetic head 
mounting plate 102 is returned to its original position, the torque 
transmission path from the motor to both reel shafts, is interrupted. 
Whereas the conventional magnetic tape recording and playback device is 
constructed in the above manner, the head mounting base plate is pulled in 
the withdrawal direction at all times, and when the head mounting base 
plate is advanced, its advancing direction is the same as the extending 
direction of the spring used for withdrawal of the head mounting base 
plate. Consequently, the more the head mounting base plate is pulled out, 
the more the pulling force to pull out the head mounting base plate is 
increased. When the head mounting base plate is pulled out, it is 
necessary to resist the force of the spring used for withdrawing the head 
mounting base plate. Accordingly, it is necessary to provide a spring 
having a very high modulus of elasticity. Therefore, in the case of tape 
recording and playback, it is necessary to pull out and hold the magnetic 
head mounting base plate, resisting the maximum spring force which 
includes the maximum tension of the head mounting base plate withdrawal 
spring, and the spring force corresponding to the deflection of the head 
mounting base plate pulling spring. The conventional device has the above 
problems. 
SUMMARY OF THE INVENTION 
The present invention has been achieved to solve the above problems. It is 
an object of the present invention to provide a magnetic tape recording 
and playback device characterized in that: the head mounting base plate 
drive springs are integrated into one unit; a spring force can be 
individually given in each case of the time of tape recording and playback 
and the time of head withdrawal; and the spring force can be determined to 
a minimum in the movement of the head mounting base plate such as advance 
and withdrawal of the head, so that the drive force of the head mounting 
base plate can be reduced. 
The present invention provides a magnetic tape recording and playback 
device comprising: a head base to which a magnetic head is attached for 
recording and playing back a cassette tape, the head base being capable of 
moving on a main base; a resilient body provided on the head base; and a 
lever having two ends, the first end of which is engaged with a groove 
formed on a disk-shaped cam for moving the head base, and the second end 
of which is engaged with the head base directly or through the resilient 
body. 
Also, the present invention provides a magnetic tape recording and playback 
device comprising: a head base to which a magnetic head is attached for 
recording and playing back a cassette tape, the head base being capable of 
moving on a main base; a drive plate having two ends, the first end of 
which is engaged with a groove formed on a disk-shaped cam provided on the 
main base for moving the head base, the drive plate being capable of 
moving in a radial direction of the disk-shaped cam when the groove is 
moved; and a resilient body engaged with both the drive plate and head 
base at two points located in the movement direction. 
Also, the present invention provides a magnetic tape recording and playback 
device comprising: a head base to which a magnetic head is attached for 
recording and playing back a cassette tape, the head base being capable of 
moving on a main base; a resilient body provided on the head base; and a 
lever, having two ends, the first end of which is engaged with a groove 
formed on a disk-shaped cam, the groove being used for moving the head 
base, and the second end of which is engaged with the head base through 
the resilient body. 
According to the present invention, in the case where the head is 
withdrawn, when the second end of the lever directly engages with the head 
base and pushes it, the head base is pushed in a direction in which the 
head being separated from the attached cassette tape, and at the same time 
one end of the resilient body engages with the engaging portion on the 
main base, so that a resilient force is given in a direction opposite to 
the direction in which the head is separated from the attached cassette 
tape. In the case of tape recording and playback, the second end of the 
lever pushes the head base through the resilient body in a direction in 
which the attached cassette tape is pressed, and during an interval 
between the time of head withdrawal and the time of recording and playing 
back a tape, the pushing force is reduced. 
Also, according to the present invention, in the case of head withdrawal, 
when the lever is moved in the radial direction, the resilient body pushes 
the head base in a direction in which the head is separated from the 
cassette tape attached to the head base. In the case of tape recording and 
playback, the resilient body pushes the head in a direction in which the 
head is pressed against the attached cassette tape when the lever is moved 
in the radial direction and also moved in the opposite direction, and 
during an interval between the time of head withdrawal and the time of 
recording and playing back a tape, the pushing force is reduced. 
According to the present invention, in the case of head withdrawal, the 
second end of the lever is engaged with the head base through the 
resilient body so that the head base is pushed. Therefore, the head base 
is pushed in a direction in which the head is separated from the attached 
cassette tape while a reaction force corresponding to the pushing force is 
being given by the resilient body. In the case of tape recording and 
playback, when the second end of the lever pushes the head base through 
the resilient body, the head is pressed against the attached cassette tape 
while a reaction force corresponding to the pushing force is being given 
by the resilient body, and the pushing force is reduced during an interval 
between the time of head withdrawal and the time of recording and playing 
back a tape.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Embodiment 1 
FIG. 10(a) is an overall perspective view of the magnetic tape recording 
and playback device of the present invention. FIG. 10(b) is a plan view 
showing the entire inventive portion. FIGS. 1, 2 and 3 are plan views 
showing an embodiment of the present invention. FIG. 1 shows a withdrawal 
condition of the head, FIG. 2 shows a movement condition of the head, and 
FIG. 3 shows a recording and playback condition of the head. In the 
drawings, numeral 10 is a magnetic head (also referred to as a head), 
numeral 20 is a magnetic head mounting base plate (also referred to as a 
head base), numerals 11, 12 are engaging members for engaging the magnetic 
head 10 with the magnetic head mounting base plate 20, numerals 21, 22, 23 
denote a spring hook integrated with the magnetic head mounting base plate 
20, numerals 24, 25, 26 are sliding guide holes formed in the longitudinal 
direction of the magnetic head mounting base plate 20, numerals 24a, 26a 
are advance stopper sections of the magnetic head mounting base plate, 
numeral 27 is an end surface for driving the magnetic head mounting base 
plate, numeral 30 is a drive lever of the magnetic head mounting base 
plate (the drive lever is also referred to as a lever), numeral 31 is a 
pin vertically provided on the drive lever 30, numeral 32 is a lever end 
surface A which is a contact portion where the drive lever 30 and spring 
40 are contacted, numeral 33 is a lever end surface B which is a contact 
portion between the drive lever 30 and the end surface 27 of the magnetic 
head mounting base 20, numeral 34 is a rotary shaft of the drive lever 30, 
numeral 40 is a spring for pressing the magnetic head mounting base plate 
(the spring is also referred to as a resilient body), numeral 41 is a fore 
end portion of the spring in the longitudinal direction, numeral 42 is a 
spring portion hooked by the spring hook 22, numeral 50 is a disk-shaped 
rotary cam gear having a cam groove (the disk-shaped rotary cam gear is 
also referred to as a disk-shaped cam), numeral 51 is a groove portion 
used for recording and playing back of a magnetic tape, numeral 52 is a 
groove portion for withdrawing the magnetic tape, numerals 53, 53a are 
groove portions for moving the head, numeral 60 is a deck base (the deck 
base is also referred to as a main base), numeral 61 is a plate member 
vertically provided on the deck base for engaging the spring used for 
pressing the head base plate mounting base, and numerals 62, 63, 64 are 
guide pins for guiding the magnetic head mounting base plate 20. 
In the magnetic tape recording and playback device constructed in the 
manner described above, in the case where the head is in the withdrawal 
condition as shown in FIG. 1, the center of the drive lever 30 is 
regulated by the rotary shaft 34, and the pin 31 vertically provided on 
the drive lever is engaged with and regulated by the groove portion 52 for 
withdrawing the head of the rotary cam gear 50, so that the position of 
the drive lever 30 can be determined. At this time, the lever end surface 
B 33 comes into contact with the end surface 27 for driving the magnetic 
head mounting base plate, so that the position of the magnetic head 
mounting base plate 20 can be regulated in the advance direction. At this 
time, the position of the spring 40 is regulated with respect to the plane 
and height directions by the hooks 21, 22, and the height of the spring 40 
is regulated by hook 23 so that the spring 40 is previously pushed in the 
opening direction. The fore end portion 41 of this spring 40 is engaged 
with and pressed by the plate member 61 vertically provided on the deck 
base. Therefore, the magnetic head mounting base plate 20 is pushed in the 
advance direction. 
Also, the position of the magnetic head mounting base plate 20 is regulated 
in the transverse direction by the action of the guide grooves 24, 25, 26. 
As a result of the foregoing, the position of the magnetic head mounting 
base plate 20 is regulated and fixed. Under the condition described above, 
the pin 31 gives a load to the groove 52 of the gear 50 in the direction 
of the gear center 58. 
Next, the head movement condition shown in FIG. 2 will be explained as 
follows. 
When the drive motor and drive gear (not shown) are rotated in the 
condition shown in FIG. 1, the rotary cam gear 50 is rotated 
counterclockwise. In this way, the condition shown in FIG. 1 is changed to 
the condition shown in FIG. 2. When the rotary cam gear 50 is rotated in 
this way, the drive lever 30 is rotated counterclockwise, and the head 
mounting base plate 20 advances. 
In FIG. 2, when the pin 31 vertically provided on the drive lever is 
engaged with and regulated by the groove 53 for moving the head of the 
rotary cam gear 50, the position of the drive lever 30 can be determined. 
At this time, the spring 40 previously pushed in the opening direction is 
regulated and fixed by the spring hook 23 integrated with the magnetic 
head mounting base plate. Further, the lever surfaces A32 and B33 of the 
lever 30 are provided in an engaging portion by the action of the fixed 
spring 40 and the end surface 27 for driving the magnetic head mounting 
base plate. Therefore, the position of the magnetic head mounting base 
plate 20 can be regulated in the transverse direction. 
As described above, the lever 30 is provided in an engaging portion by the 
action of the spring 40 and the magnetic head mounting base plate drive 
end surface 27. Therefore, under the above condition (in the section 
between the head withdrawal and the movement, and also in the section 
between the movement and the recording and playback), the load given to 
the lever 30 can be minimized, and further the rotational load given to 
the rotary cam gear 50 can be minimized. 
Next, the tape recording and playing back condition shown in FIG. 3 will be 
explained. 
When the drive motor and drive gear (not shown) are rotated in the 
condition shown in FIG. 2 (or FIG. 1), the rotary cam gear 50 is rotated 
counterclockwise. In this way, it is changed to the tape recording and 
playback condition shown in FIG. 3. When the rotary cam gear 50 is 
rotated, the drive lever 30 is rotated counterclockwise, and the head 
mounting base plate 20 is advanced. 
In FIG. 3, when the pin 31 vertically provided on the drive lever is 
engaged with and regulated by the tape recording and playback groove 
portion 51 of the rotary cam gear 50, the drive lever 30 can be 
positioned. At this time, the magnetic head mounting base plate stoppers 
24a, 26a come into contact with the guide pins 63, 64, so that the 
advancing motion of the magnetic head mounting base plate 20 is stopped, 
and the spring 40 engaged with this magnetic head mounting base plate 20, 
previously pushed to the opening direction, is pushed to the closing 
direction by the action of the lever end surface A 32. Therefore, the 
magnetic head mounting base plate 20 is set in a tape recording and 
playback condition in which the base plate 20 is pushed forward and fixed. 
Since the lever 30 is pushed forward, the rotary cam gear 50 impresses a 
force in the outer circumferential direction with respect to the gear 
center 58, so that the rotary cam gear 50 works as a rotational load. 
Embodiment 2 
FIG. 4 is a plan view showing another embodiment. Numerals 10 to 12, 20 to 
24, 24a, 25, 50 to 53, 53a, 58, 60, 62 and 63 are the same as those shown 
in Embodiment 1. Numeral 24b is a withdrawal stopper of the magnetic head 
mounting base plate 20, numeral 28 is a base plate spring hook A of the 
magnetic head mounting base plate 20, numeral 29 is a base plate spring 
hook B of the magnetic head mounting base plate 20, numeral 35 is a drive 
plate, numeral 36 is an engaging pin to engage with the cam groove of the 
rotary cam gear 50, the engaging pin 36 being vertically provided on the 
drive plate 35, numeral 37 is a plate spring hook A of the drive plate 35, 
numeral 38 is a plate spring hook B of the drive plate, and numeral 45 is 
a tension spring, one hook of which is engaged with both the base plate 
spring hook A 28 and the plate spring hook A 37 which are adjacent to each 
other, and the other hook of which is engaged with both the base plate 
spring hook B 29 and the plate spring hook 38 which are adjacent to each 
other, so that the tension spring 45 is provided between the hooks. 
Under the head withdrawal condition shown in FIG. 4, the drive plate 35 can 
push the magnetic head mounting base plate 20 in the withdrawal direction 
when the drive plate 35 is fixed by the rotary cam gear 50 at a position 
which is more withdrawn than the base plate spring hooks A 28 and B 29 
adjacent to the plate spring hooks A 37 and B 38. At this time, the 
magnetic head mounting base plate 20 which is pushed is fixed when the 
withdrawal stopper 24 comes into contact with the guide pin 63. In this 
condition, the rotary cam gear 50 is given a force by the engaging pin 36 
in the direction of the gear rotational center 58, so that the given force 
becomes a rotational load. 
Under the condition shown in FIG. 5 in which the head is moved, the 
longitudinal position of the magnetic head mounting base plate 20 is not 
regulated by the guide pin. Therefore, the spring hooks adjacent to each 
other are arranged at the same position by the action of the tension 
spring 45, so that no load is given to the rotary cam gear 50. 
Accordingly, the rotational load of the gear can be minimized. 
At the tape recording and play back position shown in FIG. 6, the drive 
plate 35 is fixed by the rotary cam gear 50 at a position which is more 
advanced than the base plate spring hooks A 28 and B 29 adjacent to the 
plate spring hooks A 37 and B 38. Therefore, the magnetic head mounting 
base plate 20 can be pushed in the advance direction. At this time, the 
pushed magnetic head mounting base plate 20 is fixed when the advance 
stopper 24a comes into contact with the guide pin 63. Under this 
condition, the rotary cam gear 50 is given a force by the engaging pin 36 
in an outer direction with respect to the rotational center 58, so that 
this force becomes a rotational load. 
Embodiment 3 
FIG. 7 is a plan view showing another embodiment. Numerals 10 to 12, 20 to 
26, 30, 31, 34, 50 to 53, 60 to 64 are the same as those shown in 
Embodiments 1 and 2. Numeral 27a is a post vertically provided on the 
magnetic head mounting base plate 20, numeral 39 is a drive spring 
engaging hook provided on the lever 30, numeral 46 is a drive spring 
hooked at the drive lever wherein the drive spring 46 is previously pushed 
in a direction so that its opening angle is directed in a closing 
direction, numeral 47 is a drive portion of the drive spring 46 used in 
the case of tape recording and playback operation. Numeral 48 is a drive 
portion of the drive spring 46 in the case of withdrawal of the head. The 
drive spring 46 is installed in such a manner that the post 27a and the 
hook 39 are interposed between the drive portions 47 and 48 formed into 
the forked construction. 
In the head withdrawal condition shown in FIG. 7, when the vertically 
provided post 27a is pushed by the head withdrawal drive portion 48 of the 
drive spring 46 in the withdrawal direction, the magnetic head mounting 
base plate 20 is fixed by the contact of the withdrawal stopper 24b and 
the guide pin 63. Under the above condition, a force is given to the 
rotary cam gear in a direction of the gear center 58, so that the force 
becomes a rotational load. 
In the head movement condition shown in FIG. 8, the position of the 
magnetic head mounting base plate 20 is not longitudinally regulated by 
the guide pin. Therefore, the drive spring is in the most closed 
condition, so that the loads of the drive lever 30 and rotary cam gear 50 
are minimized. 
In the type recording and playback condition shown in FIG. 9, when the 
vertically provided post 27a is pushed by the tape recording and playback 
drive section 47 of the drive spring 46 in the advance direction, the 
magnetic head mounting base plate 20 is fixed by the contact of the 
advance stopper 24a and the guide pin 63. 
Under the above condition, a force is given to the fixed cam gear in a 
direction outside of the gear center 58, so that the force becomes a 
rotational load. 
As described above, according to the present invention, the head base is 
positively pushed in one direction by the lever and resilient body at the 
time of head withdrawal and also at the time of recording and playing back 
a tape, and while the head base is being moved in an interval from the 
time of head withdrawal to the time of recording and playing back a tape, 
this pushing force can be reduced.