Rotary head cylinder for video tape recorder

Described herein is a rotary head cylinder assembly including a fixed lower cylinder for guiding travel of a magnetic tape, an upper cylinder rotatably mounted on the lower cylinder and provided with a number of magnetic heads, and a circuit board fixedly mounted on the upper cylinder and supporting thereon amplifiers in positions in close proximity to the respective magnetic heads. The circuit board is provided with notched portions at the outer periphery to permit direct access to screws for adjusting the height of the magnetic heads as well as to holes for adjusting the position of the magnetic heads from above the top side of the cylinder, while preventing interference by undesirable signals.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a rotary head cylinder assembly for use on a 
video tape recorder or the like, and more particularly to a rotary head 
cylinder assembly of the type which has recording and playback amplifiers 
mounted thereon. 
In the conventional rotary head cylinder assemblies of this sort, it has 
been the usual practice to divide the amplifier circuit board into two 
separate circuit boards one for the recording amplifiers and the other one 
for the playback amplifiers, mounting the two circuit boards on an upper 
cylinder, for example, on the opposite sides of an intermediate flat 
portion between the inner and outer peripheries of the upper cylinder. 
An example of such conventional rotary head cylinder assemblies is 
described in Laid-Open Japanese Patent Application 62-208409. 
The rotary head cylinder has the magnetic heads mounted thereon in 
diametrically opposite positions or in positions with a phase difference 
of 180.degree. from each other, so that it invariably requires adjustments 
of the magnetic heads into the opposite positions as well as adjustments 
for equalizing or levelling the magnetic head heights. 
The recording and playback amplifier circuit boards in the above-mentioned 
prior art device are substantially same as the upper cylinder in size, so 
that it has been necessary to adjustment the magnetic heads into the 
180.degree. positions and to a predetermined height before mounting the 
circuit boards on the upper cylinder. Once the circuit boards are fixed on 
the upper cylinder, the adjustments of the magnetic heads into the 
180.degree. positions and into level positions become very troublesome 
because the circuit boards have to be removed prior to such adjustments. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a rotary head cylinder 
assembly of the sort mentioned above, which is so constructed as to 
facilitate the adjustment of the magnetic heads into predetermined angular 
and level positions. 
It is another object of the present invention to provide a rotary head 
cylinder assembly which is easy to assemble and less susceptible to 
interference of unnecessary signals. 
It is still another object of the present invention to provide a rotary 
head cylinder assembly which permits to replace an upper cylinder without 
removing a circuit boards with amplifiers located in positions in close 
proximity to the magnetic heads. 
In order to achieve the above-stated objects, the rotary head cylinder of 
the invention has the following features separately or in combinations. 
(1) Notches are provided in outer peripheral portions of a circular circuit 
board with recording and playback amplifiers located in the proximity of 
magnetic heads; 
(2) Wiring patterns and wire threading holes are provided in notch-free 
outer peripheral portions of the circuit boards; 
(3) The circuit board is located on the inner of a flange at the outer 
periphery of the upper cylinder; 
(4) The notches of the circuit board are positioned to register with 
positions of magnetic head height adjusting screws on the upper cylinder; 
and 
(5) The head height adjusting screws are located on the upper cylinder side 
by side with magnetic head indexing holes within the areas of the notches 
in the circuit boards. 
In accordance with the present invention, the circular circuit board with 
recording and playback amplifiers in the proximity of the magnetic heads 
are provided with notches at its outer periphery in positions registering 
with positions of magnetic head levelling screws, thereby permitting to 
insert a universal driver from the top side of the rotary head cylinder 
for adjustment of the height of the magnetic heads. Besides, the 
adjustment for the 180.degree. indexing of the magnetic heads can be made 
simply by inserting an eccentric pin through the notches into indexing 
holes which are located within the areas of the notches in the circuit 
board. Further, the circuit board is provided with wiring patterns to be 
connected to the magnetic heads along with wire threading holes in outer 
peripheral areas between the notches so that the signal lines from the 
magnetic heads can be passed vertically through the wire threading holes 
in an extremely facilitated manner in the assembling process. Accordingly, 
the upper cylinder can be replaced without necessitating removal of the 
circuit board from the upper cylinder. In addition, the centering of the 
circuit board on the upper cylinder is facilitated by the use of arcs 
along the outer periphery or the inner periphery of the circuit board.

DESCRIPTION OF PREFERRED EMBODIMENTS 
Referring to the accompanying drawings, FIGS. 1 and 2 show an embodiment of 
the rotary head cylinder assembly according to the invention by way of a 
top view of the rotary head cylinder assembly and a sectional view taken 
on line X--X', respectively, the rotary head cylinder assembly including 
an upper cylinder 4 with magnetic heads 5 fixed thereon by screws 30, a 
lower cylinder 6 which guides the travel of a magnetic tape (not shown), 
and a motor 7 for rotating the upper cylinder 4. The upper cylinder 4 is 
rotated through bearings 8, rotational shaft 1 and disc 2. 
The upper cylinder 4 is fixed on the disc 2 by screws 31a and 31b. Fixedly 
mounted on top of the upper cylinder 4 is a circuit board 3 which supports 
thereon recording and playback amplifiers 9a to 9f in positions in close 
proximity to the magnetic heads. The circuit board 3 is located on the 
inner side of a flange 50 at the outer periphery of the upper cylinder 4 
in such a manner as to form gap spaces 33a to 33f of the same lengths 
between the arcs 32 at the outer periphery of the circuit board 3 and the 
inner periphery of the outer flange 50. Consequently, the circuit board 3 
is positioned concentrically with the upper cylinder 4. 
Provided on the upper cylinder 4 are connecting terminals 14 which are 
connected to the magnetic heads 5 to transfer signals to the circuit board 
3. These connecting terminals 14 interconnect the patterns formed in the 
proximity of the outer periphery of the circuit board 3 with holes 34a to 
34e. FIG. 3 shows the details of one of the connecting terminals 14. The 
upper portions 14a of the connecting terminals 14 are inserted in the 
holes 34a to 34e of the circuit board 3, and connected to the magnetic 
heads 5 at the respective lower ends 14b. 
Also provided on the upper cylinder 4 are height adjusting screws 11a to 
11f for the magnetic heads 5, along with indexing holes 35a to 35e which 
are located on the opposite sides of each one of the height adjusting 
screws 11a to 11f, respectively. The circuit board 3 is provided with 
notches 36a to 36f at its outer periphery at the positions corresponding 
to the respective sets of the height adjusting screw 11 and indexing holes 
35 (or at the positions in phase with the latter when seen in the 
direction of arrow A). 
At the time of turning the screws 11a to 11f for adjustment of the height 
of the magnetic heads, these screws can be directly accessed by inserting 
a screwdriver through the notches 36a to 36f in the circuit board 3 which 
is fixedly mounted in position on the upper cylinder. The holes 35a to 35e 
on the opposite sides of the height adjusting screws 11 are located in 
such positions that one can see, through the holes 35, the edges 38 of 
bases 5a on which the magnetic heads are bonded, when viewed in the 
direction of arrow A. Accordingly, the adjustment for 180.degree. indexing 
of the magnetic head position can be made by turning an eccentric pin (not 
shown) which is inserted in a hole 35 through a notch of the circuit board 
3. 
The above-described arrangements permit to make the necessary adjustments 
for levelling and 180.degree. indexing of the magnetic head positions 
without removing the circuit board 3 from the upper cylinder 4. Besides, 
the vertical connections of the magnetic heads 5 with the circuit board 3, 
which has the recording and playback amplifiers 9a to 9f in the proximity 
of the respective magnetic heads, not only facilitate the assembling work 
but also permit to shorten the signal lines to prevent interference by 
unnecessary signals. 
FIGS. 4 and 5 illustrate another embodiment of the invention in a top view 
and a sectional view taken on line X--X', respectively. This embodiment is 
arranged to increase the effective usable area of the circuit board 3 and 
to improve the accuracy of the rotational center of the circuit board 39 
by fitting the center opening 39 on the disc 2 which rotates with the 
rotational shaft 1. 
More specifically, the circuit board 3 of this second embodiment has an 
increased effective area which is greater by 20% than that of the circuit 
board of the first embodiment, and therefore is capable of mounting a 
larger number of circuit elements thereon. In addition it is easier to 
control the dimensional accuracy of the center opening 39 of the circuit 
board 3 as compared with the diameter of its outer periphery, and a small 
clearance suffices to fit the board 3 on the disc 2. Therefore, the 
imbalanced rotation of the cylinder assembly which might occur as a result 
of mounting of the circuit board 3 can be suppressed to a minimum and 
corrected by an easy machining operation. In the second embodiment, the 
notches 36a to 36f at the outer periphery of the circuit board 3 and the 
wiring holes 34a to 34l are located substantially on the same circle, and 
the outer peripheral portions 55a to 55f only need to have dimensions 
which are necessary for forming the patterns around the wiring holes 34. 
FIG. 6 shows the rotary head cylinder assembly of the invention in a 
sectional view taken along line X--X' of FIG. 1 to explain the manner of 
adjusting the height of one of the magnetic heads. Namely, the height of 
the magnetic head is adjusted by turning an adjusting screw 11 with a 
screwdriver which is inserted through a corresponding one of the notches 
36a to 36e while measuring the height of the magnetic head laterally by 
means of a microscope (not shown). By this adjustment, each magnetic head 
can be set at an optimum height on the upper cylinder 4 of the rotary head 
cylinder which is in assembled state including the circuit board 3. 
FIG. 7 shows the rotary head cylinder of the invention in a sectional view 
taken on line X--Y of FIG. 1 to explain the manner of making an adjustment 
for 180.degree. indexing of one of the magnetic heads by means of an 
eccentric pin 110 which is inserted in the corresponding one of the holes 
35a to 35l in the upper cylinder 4. Thus, the adjustments for 180.degree. 
indexing of the magnetic heads can be made through the circuit board 3 
which is mounted on the upper cylinder 4. 
It will be appreciated from the foregoing description that the rotary head 
cylinder construction according to the present invention permits to make 
the adjustments of the magnetic head height and 180.degree. indexing 
without requiring removal of the circuit board which carries recording and 
playback amplifiers in the proximity of the respective magnetic heads to 
prevent interference by unnecessary signals. The arcuate notches at the 
outer periphery of the circuit board as well as the notched inner 
periphery conforming with the disc in size and shape serve as a 
positioning means when mounting the circuit board on the upper cylinder. 
Nevertheless, the upper cylinder can be detached from the disc together 
with the circuit board which is mounted on the cylinder.