Rotary cylinder power feeding apparatus

A rotor rotating integrally with the rotary cylinder is rotatably fitted to a supporting member. A conductive member is arranged on the outer peripheral surface of this rotor. A conductive connecting terminal connectable with the power generating part is arranged at one end of the supporting member and a conductive brush for feeding voltage from the power source generating part to the electronic circuit through the above mentioned conductive member is arranged at the other end of the supporting member. By fitting the supporting member to the chassis without using lead wires and soldering, the power source voltage from the power generating part will be able to be fed to the electronic circuit within the rotary cylinder and the power feeding apparatus will be able to be very easily fitted to the rotary cylinder. Further, a center angle of one conductor of a plurality of conductors forming the conductive members is formed to be larger than the tape winding angle on the rotary cylinder and the lead wires and connectors are arranged near the magnetic head. Therefore, the joint between the plurality of conductors does not contact the conductive brush when the magnetic head is in contact with the magnetic tape, so that electronic noise generated when the joint between the conductors contacts the conductive brush will not affect the recorded and reproduced signals.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to rotary cylinder power feeding apparatus to be 
used for such magnetic recording and reproducing apparatus as, for 
example, video tape recorders (which shall be mentioned as VTR 
hereinafter) and more particularly to a rotary cylinder power feeding 
apparatus which is formed by facilitating the work of assembling a 
commutator forming a rotary cylinder power feeding apparatus and 
integrating such conductive members as the above mentioned commutators and 
brushes for feeding power to an electronic circuit within the rotary 
cylinder from the body so that efficiency, electric performance and 
reliability as of the apparatus may be improved. 
2. Description of the Related Art 
Generally, in magnetic recording and reproducing apparatus such as a VTR, a 
helical scanning system is used wherein a head is rotated to make a 
magnetic memory or reproduction. 
In a VTR with such a helical scanning system, for example, during 
reproduction, when at least two heads fitted on a rotary drum are rotated 
to slide helically against the running direction on a magnetic memorizing 
medium in which a signal has been magnetically memorized, the signal will 
be obtained from this magnetic memorizing medium, amplified to a 
predetermined level by an electronic circuit cush as a reproducing 
amplifier, and fed to a reproducing circuit through a contactless rotary 
transformer (which shall be mentioned as a rotary transformer hereinafter) 
so as to be reproduced. Also, during recording in a VTR, the signal to be 
memorized will be fed through the rotary transformer, the voltage and 
current required for the recording will be fed to the above mentioned head 
by a electronic circuit, such as a recording amplifier, and the head will 
rotate to slide helically on the above mentioned recording medium to 
magnetically memorize the signal. 
In a VTR, as the rotary transformer is interposed between the magnetic head 
and the circuit feeding the signal to be recorded to this magnetic head or 
amplifying the signal reproduced by the head, the signal transmitting loss 
will be large. Various suggestions have been already made as to how this 
loss should be reduced. One of the suggestions is, as described above, to 
arrange an electronic circuit to include a reproducing amplifier or 
recording amplifier between the rotary transformer and magnetic head. 
When an amplifier is provided between the rotary transformer and the 
magnetic head as mentioned above, it is necessary to feed power to the 
amplifier when a signal is reproduced or recorded, in order to amplify the 
reproduced signal or recorded signal from the magnetic head. However, in 
such case, the amplifier will be arranged within the rotary cylinder and 
will rotate together with the rotary cylinder. Therefore, in order to 
always securely feed power to the amplifier, an apparatus is required 
which is capable of feeding power from the body of the VTR to the 
preamplifier electronic circuit of the rotary cylinder, that is, a 
so-called rotary cylinder power feeding apparatus. 
A rotary cylinder power feeding apparatus of this nature generally includes 
a commutator as a conductive member which has two positive and negative 
pole devices connected through lead wires with the electronic circuit of 
the amplifier provided within the rotary cylinder. The power feeding 
apparatus is axially fitted to the shaft of the rotary cylinder through a 
connecting and fixing member (which shall be mentioned as a coupling 
hereinafter) and rotates together with the rotary cylinder, and has 
positive pole and negative pole conductive members (which shall be 
mentioned as conductive brushes or merely brushes hereinafter) which are 
arranged to correspond respectively to the positive and negative poles of 
the rotating commutator and will feed power from the body when they 
contact the respective outer peripheries of the commutator. 
The commutator is generally formed of a stay and a cylindrical conductive 
member fitted to this stay. This cylindrical conductive member is arranged 
to contact the positive and negative pole brushes on the outer periphery 
of the stay and is formed by pressing. When the stay of the commutator is 
fitted with a coupling fixed on the upper surface of the rotary cylinder 
to rotate coaxially with the above mentioned rotary cylinder, it will be 
positioned coaxially with the rotary cylinder. 
The brush is generally formed by having the positive and negative pole 
conductive members fitted to a supporting member. This brush supporting 
member is made to contact the rotating positive and negative commutators 
with a predetermined contact pressure by an arm fixed to a main base and 
is held in a predetermined position. 
The commutators and such preamplifier electronic circuit arranged within 
the rotary cylinder are connected by lead wires, such that the commutators 
are connected by a connector through lead wires from the lower ends of the 
commutators. The connector is connected to a connector connecting hole 
provided on the upper surface of the rotary cylinder. Alternatively, the 
connector connecting hole on the upper surface of the rotary cylinder may 
be provided with a connecting device connected with the electronic circuit 
part as of the preamplifier provided within the rotary cylinder. When the 
connector is inserted into this connecting device, the power from body 
will be fed to the electronic circuit of the preamplifier through the 
above mentioned brush, commutator and connector. 
However, in the conventional rotary cylinder power feeding apparatus 
because the commutator used for the rotary cylinder power feeding 
apparatus is formed by simultaneously inserting a cylindrically formed 
commutator onto the commutator shaft (which is fitted to the rotary 
cylinder shaft) and pressing it onto the shaft, assembly is complicated 
and the cost is high. Also, in order to cylindrically form the commutator, 
the type of material used as the conductive member is limited. Further, 
the conductive member must be formed by a special producing method and 
therefore its productivity will be greatly influenced. 
Also, the commutator shaft must be directly fixed to the rotary cylinder or 
a connecting member must be used to couple the commutator shaft so that it 
is axially fitted within the rotary cylinder. However, in the case of this 
fixing and fitting work, the commutator shaft will have to be coaxially 
fitted to the above mentioned rotary shaft and, at the same time, the 
contact position in the vertical direction with the above mentioned brush 
will have to be determined. As a result, the assembling work will be 
complicated and the productivity will be greatly influenced. 
Further, the above mentioned commutator and the preamplifier electronic 
circuit arranged within the rotary cylinder have been connected with each 
other by means of a connector connecting them through the above mentioned 
commutator and lead wires. However, in this connecting method, the 
vicinity of the connector connecting hole on the upper surface of the 
rotary cylinder is so precisely formed that the fitting work is 
complicated. Additionally, the fitted lead wire type connector will rotate 
at a high speed with the rotary cylinder. Therefore, problems occur with 
contact or entanglement of the wires with the rotary cylinder or breakage 
of the lead wires and the lead wires must be bound to prevent such 
trouble. When the connection between the wire type connector arranged in 
the connecting hole and the preamplifier electronic circuit is made by 
using another connector, such as when the lead wire type connector is used 
simultaneously, there will be two connections and the connecting and 
assembling work will be complicated. Moreover, because the commutator 
shaft is fixed to the upper surface of the rotary cylinder directly or 
with a coupling, maintenance becomes inconvenient. 
SUMMARY OF THE INVENTION 
An object of the present invention is to provide a rotary cylinder power 
feeding apparatus wherein the commutator assembling work can be made easy. 
Another object of the present invention is to provide a rotary cylinder 
power feeding apparatus wherein the position of the commutator for the 
rotary cylinder shaft and brush can be determined by a simple formation. 
Another object of the present invention is to provide a rotary cylinder 
power feeding apparatus wherein the commutator can be connected to such 
electronic circuit as of the preamplifier without increasing the number of 
the component parts and losing the reliability. 
Another object of the present invention is to provide a rotary cylinder 
power feeding apparatus wherein, in case the power feeding apparatus is 
formed separately from the rotary cylinder, the rotary cylinder rotating 
operation will be transmitted to the power feeding apparatus so that the 
power may be securely fed. 
Another object of the present invention is to provide a rotary cylinder 
power feeding apparatus wherein a countermeasure against noise is applied 
to the rotary power fed by the commutator and brush. 
The rotary cylinder power feeding apparatus according to the first 
embodiment includes: 
a rotary cylinder provided with a magnetic head and an electronic circuit 
to be connected to the magnetic head; 
a columnar rotor rotating integrally with the rotary cylinder; 
conductive members each comprising a plurality of conductors arranged in 
such a state as divided in a circumferential peripheral direction on an 
outer peripheral surface of this rotor and electrically connected to the 
above mentioned electronic circuit; and 
conductive brushes fitted to contact these conductive members and feeding a 
power to the above mentioned electronic circuit through the above 
mentioned conductive members. 
According to the first embodiment, when the conductive member arranged on 
the outer peripheral surface of the columnar rotor rotating integrally 
with the rotary cylinder is separated into a plurality of parts, for 
example, three parts, in said conductive member assembling work, the above 
mentioned separated conductive member parts will be able to be assembled, 
for example, by being pasted to the above mentioned columnar rotor from 
the side without being fitted in so that the conductive member assembling 
work may be easy. 
The rotary cylinder power feeding apparatus according to the second 
invention comprises: 
a rotary cylinder provided with a magnetic head and an electronic circuit 
to be connected to this magnetic head; 
a rotary driving member rotating integrally with this rotary cylinder; 
a columnar rotor supported by a supporting member coaxially with the above 
mentioned rotary driving member, separately from the above mentioned 
rotary driving member and rotatably; 
conductive members provided on the outer peripheral surface of the above 
mentioned rotor and electrically connected to the above mentioned 
electronic circuit; 
conductive brushes provided on the above mentioned supporting member, 
contacting the above mentioned conductive members and feeding a power to 
the above mentioned electronic circuit; and 
a rotation transmitting means provided between the above mentioned rotary 
driving member and the above mentioned rotor and transmitting the rotation 
of the above mentioned rotary driving member to the above mentioned rotor. 
According to the second embodiment, when the rotation transmitting member 
fitted between the columnar rotor forming the rotary shaft of the above 
mentioned electric conductive member and the rotary driving member and the 
rotary driving member rotating integrally with the rotary shaft of the 
rotary cylinder are engaged with each other, the rotary cylinder rotating 
operation will be able to be securely transmitted to the columnar rotor 
and the relative positions in the vertical direction of the above 
mentioned conductive member and conductive brush will be able to be well 
determined. 
The rotary cylinder power feeding apparatus according to the third 
embodiment comprises: 
a rotary cylinder provided with a magnetic head and an electronic circuit 
to be connected to said magnetic head and rotated and driven as rotatably 
provided for against (or opposite) a fixed cylinder fixed to a chassis; 
a supporting member provided with two ends, removably fitted at one end to 
a fitting member provided in the above mentioned chassis and supporting at 
the other end a columnar rotor so as to rotate integrally with the above 
mentioned rotary cylinder; 
conductive members provided on the outer peripheral surface of the above 
mentioned rotor and electrically connected with the above mentioned 
electronic circuit when the above mentioned supporting member is fitted to 
the above mentioned chassis; 
conductive connecting terminals arranged at one end of the above mentioned 
supporting member and electrically connected with a power feeding terminal 
provided opposite the above mentioned chassis when the above mentioned 
supporting member is fitted to the above mentioned chassis; and 
conductive brushes arranged at the other end of the above mentioned 
supporting member, contacting the above mentioned conductive members as 
electrically connected with the above mentioned conductive connecting 
terminals and feeding the power to the above mentioned electronic circuit. 
According to the third embodiment, as the rotor rotating integrally with 
the rotary cylinder is rotatably fitted to the supporting member, the 
conductive member is arranged on the outer peripheral surface of this 
rotor, the conductive connecting terminal connectable with the power 
generating part is arranged at one end of the supporting member and the 
conductive brush for feeding a voltage from the power generating part to 
the electronic circuit through the above mentioned conductive member is 
arranged at the other end of the supporting member, without using such 
means as the lead wires and soldering, by only fitting the supporting 
member to the chassis, the supply source voltage from the power generating 
part will be able to be fed to the electronic circuit within the rotary 
cylinder through the conductive brush and the conductive member connected 
with the conductive brush and the power feeding apparatus will be able to 
be very easily fitted to the rotary cylinder. 
The rotary cylinder power feeding apparatus according to the fourth 
embodiment comprises: 
a rotary cylinder provided with a magnetic head and an electronic circuit 
to be connected to the magnetic head; 
a tape-like recording medium running as wound on this rotary cylinder and 
having information signals recorded or reproduced by the above mentioned 
magnetic head; 
a columnar rotor rotating integrally with the above mentioned rotary 
cylinder; 
conductive members comprising a plurality of conductors arranged as divided 
in a circumferential direction on an outer peripheral surface of the 
columnar rotor and electrically connected to the above mentioned 
electronic circuit; 
connecting means electrically connecting the conductive members and the 
above mentioned electronic circuit with each other; and 
conductive brushes fitted to contact the above mentioned conductive member 
and feeding a power to the above mentioned electronic circuit through the 
above mentioned conductive member, and is characterized in that: 
a center angle of one conductor of the plurality of conductors forming the 
above mentioned and divided in the circumferential direction conductive 
member is formed to be larger than a tape winding angle when the above 
mentioned tape-like recording medium is wound on the rotary cylinder; 
the above mentioned connecting means is arranged near the above mentioned 
magnetic head; and, 
in a magnetic head rotating position in which the above mentioned magnetic 
head does not detect a signal from the above mentioned tape-like recording 
medium, the above mentioned plurality of conductors are arranged on the 
outer peripheral surface of the above mentioned columnar rotor so that a 
joint part between the plurality of conductors forming the above mentioned 
conductive member may contact the above mentioned conductive brush. 
According to the fourth embodiment, as the center angle of one conductor of 
the plurality of conductors forming the above mentioned conductive member 
is formed to be larger than the tape winding angle on the rotary cylinder, 
such connecting means as the lead wires and connector are arranged near 
the magnetic head and, in a rotating position in which the magnetic head 
detects a signal from the tape-like recording medium, the above mentioned 
plurality of conductors are arranged on the outer peripheral surface of 
the above mentioned columnar rotor so that the joint part between the 
above mentioned plurality of conductors may not contact the above 
mentioned conductive brush, the electric noise generated when the joint 
part between the conductors contacts the conductive brush will not 
influence the recorded and reproduced signals of the magnetic head and the 
recording and reproducing quality in the recording and reproducing 
apparatus will be able to be improved. 
The rotary cylinder power feeding apparatus according to the fifth 
embodiment comprises: 
a rotary cylinder provided with two magnetic heads arranged as opposed to 
each other on a rotary peripheral surface of said rotary cylinder and an 
electronic circuit to be connected to said magnetic heads; 
a tape-like recording medium running as wound on this rotary cylinder and 
having information signals recorded or reproduced alternately by the above 
mentioned two magnetic heads; 
a columnar rotor rotating integrally with the above mentioned rotary 
cylinder; 
conductive members comprising a plurality of conductors arranged as divided 
in a circumferential direction on an outer peripheral surface of this 
rotor and electrically connected to the above mentioned electronic 
circuit; 
connecting means electrically connecting the above mentioned electronic 
circuit with this conductive member; and 
conductive brushes fitted to contact the above mentioned conductive members 
and feeding a power to the above mentioned electronic circuit through the 
above mentioned conductive member, 
and is characterized in that: 
a center angle of one conductor of the plurality of conductors forming the 
above mentioned conductive member and divided in the circumferential 
direction is formed to be larger than a tape winding angle when the above 
mentioned tape-like recording medium is wound on the rotary cylinder; 
the above mentioned connecting means is arranged near the first magnetic 
head of the above mentioned two magnetic heads; and 
in a first magnetic head rotating position in which the above mentioned 
first magnetic head does not detect a signal from the above mentioned 
tape-like recording medium, the above mentioned plurality of conductors 
are arranged on the outer peripheral surface of the above mentioned 
columnar rotor so that a joint part between the plurality of conductors 
forming the above mentioned conductive member may contact the above 
mentioned conductive brush. 
According to the fifth embodiment, as the center angle of one conductor of 
the plurality of conductors forming the conductive member is formed to be 
larger than the tape winding angle on the rotary cylinder, such connecting 
means as lead wires and connectors are arranged near the first magnetic 
head of the two magnetic heads and, in a rotating position in which this 
first magnetic head detects a signal from the tape-like recording medium, 
the above mentioned plurality of conductors are arranged on the outer 
peripheral surface of the above mentioned columnar rotor so that the joint 
part between the above mentioned plurality of conductors may not contact 
the above mentioned conductive brush, therefore the electric noise 
generated when the joint part between the conductors contacts the 
conductive brush will not influence the recorded and reproduced signals of 
the magnetic head and the recording and reproducing quality in the 
recording and reproducing apparatus provided with two or more magnetic 
heads will be able to be improved. In this case, as the other magnetic 
head than the first magnetic head is in a position separate from the 
connecting means which is a noise generating source, when the other 
magnetic head detects a signal, even if an electric noise is generated, 
the electric noise will be harder to mix into the other magnetic head than 
the first magnetic head.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The preferred embodiments will now be explained with reference to the 
drawings. 
FIGS. 1 to 4 show the first embodiment of a rotary cylinder power feeding 
apparatus according to the present invention. FIG. 1 is a general 
formation view showing the formation of a VTR using a rotary cylinder 
power feeding apparatus. FIG. 2 is a block diagram showing the principle 
of the rotary cylinder power feeding apparatus shown in FIG. 1. FIG. 3 is 
a side view of a VTR main part showing the formation of a rotary cylinder 
power feeding apparatus according to the present invention. FIG. 4 is a 
perspective view showing the formation of a commutator. 
As shown in FIG. 1, a VTR 1 is provided with a cassette holder 2 which 
carries in a cassette tape (not illustrated) and carries the cassette tape 
to a predetermined position as a preparing step for loading the tape. The 
cassette tape carried by this cassette holder 2 is set in a predetermined 
position within the VTR 1 and is then loaded by an S (supply reel side) 
slider 3 and T (take-up reel side) slider 4. As a result, the tape pulled 
out of the cassette tape will be wound at a predetermined angle on the 
outer peripheral surfaces of a rotary cylinder 5 and fixed cylinder 6. 
Now, for example, in the case of reproduction, a video signal will be 
detected from the tape sliding on the outer peripheral surface of the 
rotary cylinder by a plurality of magnetic heads provided on the rotary 
cylinder 5, will be fed to such electronic circuit (not illustrated) as of 
a preamplifier arranged within the rotary cylinder 5 and will be amplified 
at a predetermined amplification rate. Therefore, at a better S/N ratio, 
the video signal will output from the electronic circuit preamplifier and 
will be fed to the fixed cylinder side through a rotary transformer. Then, 
the video signal will be processed by a signal processing circuit (not 
illustrated) provided on the main substrate of the body and will be able 
to be obtained as a video image and audio output. 
In order to feed power from the body to the preamplifier electronic 
circuit, as shown in FIG. 1, a rotary cylinder power feeding apparatus 7 
in this embodiment is fitted to the rotary cylinder 5 on the upper part 
and is pivoted with the shaft of the rotary cylinder 5 through a coupling. 
For example, as shown in FIG. 2, the rotary cylinder power feeding 
apparatus 7 is an apparatus for feeding power from the body to the 
electronic circuit of a preamplifier 5c arranged, for example, within the 
rotary cylinder 5. The power feeding apparatus 7 is provided with 
conductive brushes 7a and 7b having positive and negative poles connected 
with the power source apparatus of the body. When these brushes 7a and 7b 
contact respectively commutators 7c and 7d as conductive members provided 
with positive and negative poles connected with a preamplifier 5c arranged 
within the rotary cylinder 5, the power will be fed to the preamplifier 
electronic circuit and, as a result, the electronic circuit will be 
driven. Thereby, the video signal detected from the sliding tape (not 
illustrated) by the magnetic head 5a (or 5b) arranged on the outer 
periphery of the rotary cylinder 5 will be amplified by the electronic 
circuit of the preamplifier 5c, will be transmitted to the fixed cylinder 
6 side through a magnetically connected rotary transformer 56 and will be 
able to be fed to a signal processing circuit (not illustrated) provided 
in the main substrate. 
Therefore, FIG. 3 shows an example which, to eliminate the problems in the 
conventional technique, the working of assembling commutators in the 
rotary cylinder power feeding apparatus has been improved. 
As shown in FIG. 3, the rotary cylinder power feeding apparatus 7 in this 
embodiment is fixed by an arm 15 fixed to a main base 20 forming a chassis 
of the VTR 1. The arm 15 functions as a supporting member. On the other 
hand, within the rotary cylinder 5, for example, as described above, the 
electronic circuit of the preamplifier 5c is arranged and is connected to 
the commutators 7c and 7d of the rotary cylinder power feeding apparatus 7 
through lead wires 13 connected with this electronic circuit. The 
commutators 7c and 7d corresponding respectively to these positive and 
negative poles rotate together with the rotary cylinder 5 but, when a 
brush supporting member 14 holding the brushes 7a and 7b of the rotary 
cylinder power feeding apparatus 7 is fixed in a predetermined position by 
the arm 15, the brushes 7a and 7b will be able to contact the rotating 
commutators 7c and 7d under a predetermined contact pressure. Therefore, 
contact friction will not negatively influence the sliding commutators 7c 
and 7d and the conducting state will be able to be always securely 
maintained. Thereby, the power from the body will be able to be fed to the 
electronic circuit of the preamplifier 5c arranged within the rotary 
cylinder 5. 
The rotary cylinder power feeding apparatus 7 in this embodiment is 
preferably provided with a cabinet part 7e (which shall be mentioned as a 
shield cover hereinafter) shielding the rotary cylinder power feeding 
apparatus 7. In the case of FIG. 3, this shield cover is removed. 
Therefore, the above mentioned commutator 7c or 7d of the rotary cylinder 
power feeding apparatus 7 in this embodiment is characterized by being 
formed, as shown in FIG. 4, of a commutator core 70 as a columnar rotor 
provided coaxially with the rotary cylinder 5 and fitted to a fixed shaft 
12, a plurality of, or, for example, three metal pieces 71 as conductive 
members to be fitted to the outer periphery of this commutator 70, 
connecting terminals 73 to be connected to these metal pieces 71 and a 
disc member (washer) not illustrated to press and fix in the above 
mentioned commutator core 70 the above mentioned plurality of metal pieces 
71 as fitted and exposing the connecting terminals 73. 
The above mentioned metal piece 71 can be easily made by pressing, for 
example, one metal plate and, at the same time, in case the above 
mentioned shaft 12 is fixed through a coupling 8 on the upper surface of 
the rotary cylinder 5, the commutator core 70 will be first fitted to the 
above mentioned shaft 12, then the divided metal pieces will be jointed to 
the outer peripheral surface of the above mentioned commutator core 70 
from the horizontal direction and therefore the fitting work will be easy. 
Therefore, according to such formation, when the outer peripheral surface 
member as a conductive member forming the above mentioned commutators 7c 
and 7d is formed, for example, to be three metal pieces, for example, if 
the commutator core 70 is fitted in advance to the shaft 12 of the rotary 
cylinder power feeding apparatus, in the following assembling work, the 
above mentioned metal pieces 71 will be able to be respectively bonded, 
the commutator assembling work will be easy and the productivity will be 
able to be clearly expected to improve. The metal pieces 71 preferably are 
electrically connected with each other and are be connected with the 
electronic circuit through common lead wires 13. 
Also, as described above, the metal piece 71 can be easily formed, for 
example, by pressing a flat plate. Thus, no special material member is 
required. Cheap material may be used, the surface may be specially worked 
with a precious metal and the electric connecting part material may be 
extensively utilized. As a result, the reliability will be able to be 
improved. 
In this embodiment a rotary cylinder power feeding apparatus 7 is formed 
with the shield cover for shielding it. However, a conventional rotary 
cylinder power feeding apparatus without a shield cover may also be 
formed. 
FIGS. 5 and 6 show the second embodiment of a rotary cylinder power feeding 
apparatus according to the present invention. FIG. 5 is a formation view 
of a VTR main part showing the formation of a rotary cylinder power 
feeding apparatus. FIG. 6 (a) is a lower surface view of a plate spring 
member engaged with a coupling fixed to a rotary cylinder and having 
functions of transmitting the rotary cylinder rotating operation and 
holding the positioning of a commutator. FIG. 6 (b) is an upper surface 
view of a coupling engaged with the above mentioned plate spring member. 
The lower surface of the plate spring member shown in FIG. 6 (a) and the 
upper surface of the coupling shown in FIG. 6 (b) are to be opposed to 
each other. Also, in these drawings, the same components as in the first 
embodiment are indicated by the same reference numerals. 
The rotary cylinder power feeding apparatus 7 in this embodiment includes, 
for example, as shown in FIG. 5, commutators 7c and 7d formed of positive 
and negative conductive devices, brushes 7a and 7b contacting the positive 
and negative poles respectively of these commutators 7c and 7d and a 
holder 14 providing and supporting these brushes 7a and 7b with a 
predetermined width. The rotary cylinder power feeding apparatus 7 is 
formed as one package by shielding all the outside surface of this formed 
rotary cylinder power feeding apparatus 7 with the shield cover 7e and, 
even when the rotary cylinder power feeding apparatus 7 is formed as one 
package, the rotary cylinder 5 rotating operation will be securely 
transmitted through the coupling 8 as a rotating driving member, and the 
respective commutators 7c and 7d will always be positioned in a 
predetermined position. 
As shown in FIG. 5, for example, the rotary cylinder power feeding 
apparatus 7 is provided with a shaft 12 coaxial with the rotary cylinder 
5. Shaft 12 is fitted in the upper part through a metal member 16 and is 
made slidable vertically with respect to the metal member 16. On the lower 
surface of the metal member 16, a washer 17 is provided and loosely fitted 
to the shaft 12. The respective commutators 7c and 7d of the positive and 
negative poles are bonded and fixed respectively to disc members 18a and 
18b and are rotatably fitted to the above mentioned shaft 12. In this 
embodiment, the disc member 18a is arranged to be below the washer 17 and 
the disc member 18b is arranged on the rotary cylinder side. 
The commutators 7c and 7d are positioned and contacted to correspond 
respectively to the positive and negative poles of the brushes 7a and 7b. 
The brushes 7a and 7b are supported by a holder 14 and are packaged by a 
shield cover 7e enclosing the holder 14, the metal member 16 fitted to the 
upper part of the shaft 12 and the commutators 7c and 7d fitted to the 
shaft 12 and brushes 7a and 7b. The holder 14 is fixed to the main base 
through an arm 15. 
Here, as shown in FIG. 6 (a), an engaging member 19 forming at least two 
plate springs 19a and 19b as resilient pieces of a metal plate on the 
lower surface of the disc member 18b to which the negative pole commutator 
7d is fitted. The engaging member 19 forms a rotation transmitting means 
together with a later described groove 8a. These plate springs 19a and 19b 
are formed to project toward the rotary cylinder 5 side and are energized 
in the vertical direction for the engaging member 19. In the outer 
peripheral end part of this engaging member 19, the lead wires 13 
connected with the commutators 7c and 7d and a connector 21 at the tips of 
these lead wires 13 are led out through the disc member 18b. 
On the other hand, on the rotary cylinder 5 side, a coupling 8 is provided 
on the upper surface of the rotary cylinder 5 and is fitted to the shaft 
of the rotary cylinder 5 to rotate together with the rotary cylinder 5. On 
the upper surface of the coupling 8, for example, as shown in FIG. 6 (b), 
a plurality of grooves 8a engaging with the two plate springs 19a and 19b 
of the engaging member 19 are formed to form a rotation transmitting means 
together with the engaging member 19. Near the center of the upper 
surface, an axial hole 8b is formed with a predetermined depth and is 
tapered in the upper part. This hole receives the lower end of shaft 12 of 
the rotary cylinder power feeding apparatus 7 when the rotary cylinder 
power feeding apparatus 7 is fitted by the arm 15. The taper is provided 
to facilitate assembly. 
The lead wires 13 projecting out of the disc member 18b are fitted at the 
tips to a connector 21 and will be connected when the above mentioned 
connector 21 is inserted into a connector inserting hole (not illustrated) 
connected with the electronic circuit of the preamplifier arranged within 
the rotary cylinder 5. 
Now, the operation of the thus formed rotary cylinder power feeding 
apparatus shall be explained in detail with reference to FIG. 5. 
The rotary cylinder power feeding apparatus 7 is lowered from the upward 
direction of the coupling 8 borne on the upper surface of the rotary 
cylinder 5, is arranged so that the shaft 12 of the rotary cylinder power 
feeding apparatus 7 and the bearing hole 8b of the coupling 8 may join 
with each other and is fixed and fitted to the main base by the arm 15. 
In this case, in the relative positions of the brushes 7a and 7b and the 
commutators 7c and 7d of the rotary cylinder power feeding apparatus 7, by 
the vertically upward energizing force by the plate springs 19a and 19b of 
the engaging member 19 bonded to the lower surface of the disc member 18b, 
the above mentioned disc member 18b will be always pushed up, therefore 
the washer 17 loosely fitted to the shaft 12 will join with the metal 
member 16 fixed to the shield cover 7e and thereby a fixed height will be 
able to be maintained. Thereby, the brushes 7a and 7b of the commutators 
7c and 7d within the rotary cylinder power feeding apparatus 7 will be 
always stably positioned, that is to say, a positive contact state will be 
able to be held and therefore power will be able to be effectively fed. 
Therefore, when for example during reproduction, the rotary cylinder 5 will 
rotate and cause the plate springs 19a and 19b projecting out of the 
engaging member 19 on the rotary cylinder power feeding apparatus 7 side 
to engage with the plurality of grooves 8a of the coupling 8 fitted to the 
shaft of the rotary cylinder 5. Thus, the rotary cylinder 5 rotational 
motion will be transmitted to the shaft 12 of the commutators 7c and 7d 
through the grooves 8a of the coupling 8 and the plate springs 19a and 19b 
linked with these grooves 8a, so that the torque will be transmitted to 
the rotary cylinder power feeding apparatus 7. 
Thereby, when the rotary cylinder power feeding apparatus 7 is arranged to 
engage with the couplings 8 of the rotary cylinder 5 and is only fitted to 
the arm 15 fixed to the main base, the rotary cylinder 5 rotational 
operation will be easily transmitted, the commutators 7c and 7d will be 
easily positioned with respect to the brushes 7a and 7b and further the 
power from the body will be securely fed to the electronic circuit of the 
preamplifier arranged within the rotary cylinder 5. 
Therefore, in this embodiment, when the plate springs 19a and 19b are used 
as rotating power transmitting means, without using the member for 
positioning the relative positions of the commutators 7c and 7d and the 
brushes 7a and 7b and the member for transmitting the rotary cylinder 5 
rotating power, the relative positions of the commutators 7c and 7d and 
the brushes 7a and 7b will be positioned and power will be able to be 
easily transmitted to the electronic circuit within the rotary cylinder. 
Also, when the rotary cylinder power feeding apparatus 7 is packaged, not 
only the assembling work will become easy but also the productivity will 
be able to be improved. 
This embodiment the engaging member 19 is provided in the disc member 18b 
and the plurality of grooves 8a are provided in the coupling 8. However, 
the plurality of grooves may be formed in the disc member 18b and the 
engaging member 19 may be provided in the coupling 8. 
Also, the plurality of grooves engaging with the plate springs of the above 
mentioned coupling 8 may be radially provided so as to be easily meshed 
and engaged, for example, in assembling. 
FIG. 7 shows an improved example of directly connecting the rotary cylinder 
power feeding apparatus 7 and the electronic circuit of the preamplifier 
within the rotary cylinder 5 with each other without using the lead wires 
and connectors. 
FIGS. 7 and 8 show the third embodiment of a rotary cylinder power feeding 
apparatus according to the present invention. FIG. 7 is a perspective view 
showing the formation of the rotary cylinder power feeding apparatus. FIG. 
8 is a sectioned view of a VTR main part fitted with the rotary cylinder 
power feeding apparatus. FIG. 9 is a comparative sectioned view for 
explaining the rotary cylindrical power feeding apparatus shown in FIG. 8 
and showing an example of the rotary cylinder power feeding apparatus 
provided with a lead wire connecting system. 
In FIGS. 7 to 9, components the same as components in the other embodiments 
are indicated with similar reference numerals. Therefore, a duplicative 
explanation will not be given and only the different parts will be 
explained. 
As shown in FIG. 9, the rotary cylinder power feeding apparatus 7 is 
usually fixed by means of screws 40 to an outsert molded stay 28 fixed to 
the main base 20 through an arm 15c. In order to feed power to the 
electronic circuit (not illustrated) of the preamplifier arranged within 
the rotary cylinder 5 through the rotary cylinder power feeding apparatus 
7 from the power source apparatus (not illustrated) arranged on the body 
or so-called main substrate 30, it is necessary for the positive and 
negative pole lead wires 29a and 29b, connected respectively with the 
brushes 7a and 7b of the rotary cylinder power feeding apparatus 7, to be 
connected with the main substrate 30 side by means of the main substrate 
connector 30b. The lead wires 13 connected with the commutators 7c and 7d 
of the rotary cylinder power feeding apparatus 7 should also be connected 
with the preamplifier substrate 26 side within the rotary cylinder 5 by 
means of the connector 21. 
However, in such connecting method, by using the lead wires 13, 29a and 29b 
and connectors 21 and 30b, there are at least two connected parts, for 
example, the connectors. Therefore, assembly becomes complicated and, when 
the rotary cylinder 5 rotates, as it is connected by the lead wires, a 
problem can arise in that the lead wires can contact, can become entangled 
with the rotary cylinder or can be broken. 
Therefore, to eliminate these problems, this embodiment employs components 
which can be connected without using lead wires, thus simplifying 
assembly. An example of one such rotary cylinder power feeding apparatus 
is shown in FIG. 7. 
In the drawing, in order to make it unnecessary to use two lead wire 
connections as described above, the connective structure between the 
rotary cylinder power feeding apparatus 7 and the preamplifier substrate 
26 (See FIG. 8) within the rotary cylinder 5 is improved. Therefore, 
first, the connecting structure to the main substrate 30 shall be 
explained. 
The arm 15 fixing the rotary cylinder power feeding apparatus 7 in a 
predetermined position is formed to be L-shaped and is extended at the 
lower end to be of a predetermined length so as to be engaged with a main 
substrate connector 30a arranged on the main substrate 30. A conductive 
member (not illustrated) is laid within the arm 15 connected from the 
brushes 7a and 7b of the above mentioned rotary cylinder power feeding 
apparatus 7. The positive pole conductive connecting terminal 15a and the 
negative pole conductive connecting terminal 15b corresponding 
respectively to the brushes 7a and 7b are fitted to the base end of this 
conductive member, that is, to the base end of the arm 15. 
A through hole is provided in the main base 20 to receive arm 15 to engage 
at the base end with the main substrate connector 30a as a power feeding 
terminal of the main substrate 30. An outsert molded guide 20a as an arm 
fitting member for guiding and holding the arm 15 in a predetermined 
position is fitted to this through hole. 
The structure connecting to the preamplifier substrate 26 (See FIG. 8) 
within the rotary cylinder 5 is provided on the lower surface of the 
negative pole commutator 7d of the rotary cylinder power feeding apparatus 
7 with a connecting terminal 25 to be connected with this commutator 7d 
and is fitted with a shaft cap 22 which can be fitted and pivoted to the 
rotary shaft 51 of the rotary cylinder 5. This shaft cap 22 is provided at 
the lower end with a positive pole connecting terminal 24 to be connected 
with the commutator 7c. These connecting terminals 24 and 25 are extended 
by a predetermined length, for example, in the downward direction and are 
inserted through a flange cut hole 53 provided in the rotary cylinder 5 
through a cut in plate 23 secured to the lower surface of the shaft cap 
22. The plate 23 is designed to have a diameter which enables it to enter 
a hole 5d formed in the upper part of the rotary cylinder 5. As shown in 
FIG. 8, a concave hole 22a to be fitted and pivoted to the rotary shaft 51 
of the rotary cylinder 5 is formed at the lower end of the shaft cap 22 
and in the plate 23, a locking hole 22b is formed and connected to the 
above mentioned concave hole 22a and in order to positively lock the 
rotation of the rotary cylinder 5. That is to say, when the shaft cap 22 
is fitted to the rotary shaft 51 of the rotary cylinder 5, the locking 
part 51a provided near the rotary shaft 51 of the rotary cylinder 5, that 
is, near the rotary shaft 51 on the cylinder flange 52, will be fitted in 
the locking hole 22b and, when the rotary cylinder 5 rotates, the rotary 
shaft 51 and, plate 23 and shaft cap 22 will be able to be locked. 
As shown in FIG. 8, when the plate 23 secured to the lower end of the above 
mentioned rotary cylinder power feeding apparatus 7 is inserted into the 
hole 5d of the rotary cylinder 5 and is mounted on the upper surface of 
the cylinder flange 52, the plate 23 and shaft cap 22 will be inserted and 
fixed in the rotary shaft 51. When plate 23 is fitted on the upper surface 
of the cylinder flange 52, the outer peripheral surface of the plate 23 
and the inner peripheral surface of the rotary cylinder 5 will be in close 
contact with each other. In this case, the thrust will be received by the 
bottom surface of the rotary cylinder 5 and the upper surface of the 
cylinder flange 52 and the radial force will be received, as described 
above, by the outer peripheral surface of the plate 23 and the inner 
peripheral surface of the rotary cylinder 5. Therefore, such fitting 
members as, for example, fitting screws for fixing the plate 23 will be 
able to be made unnecessary. 
On the preamplifier substrate 26 fitted within the rotary cylinder 5, a 
preamplifier land 27 in direct contact with the connecting terminals 24 
and 25 is provided in a predetermined position. When the rotary cylinder 
power feeding apparatus 7 is fitted, the connecting terminals 24 and 25 
made integral with the rotary cylinder power feeding apparatus 7 will 
contact the preamplifier land 27 and will be able to be electrically 
connected. The preamplifier land 27 is connected with the electronic 
circuit of the preamplifier (not illustrated) by a printed wiring on the 
preamplifier substrate 26. 
The method of fitting the rotary cylinder power feeding apparatus will now 
be explained in detail with reference to FIGS. 7 and 8. 
First, as shown in FIG. 7, the arm 15 of the rotary cylinder power feeding 
apparatus 7 is inserted along the outsert guide 20a provided on the main 
base 20 and the positive and negative pole connecting terminals 15a and 
15b at the tip of the above mentioned arm 15 are connected respectively to 
the main substrate connector 30a provided on the main substrate 30. 
Simultaneously with this connection, connection is made to the rotary 
cylinder 5 which is a main part of the rotary cylinder power feeding 
apparatus 7. In this case, the positive and negative pole connecting 
terminals 24 and 25 projecting out of the end of the rotary cylinder power 
feeding apparatus 7 are inserted first from the diagonal direction into 
the cylinder cut hole 53 provided in the cylinder flange 52 within the 
rotary cylinder 5, are lowered toward the preamplifier substrate 26 fitted 
within the rotary cylinder 5 and are connected in contact with the 
preamplifier land 27 provided on the preamplifier substrate 26, as shown 
in FIG. 8. Also, simultaneously, the plate 23 and shaft cap 22 of the 
rotary cylinder power feeding apparatus 7 are fitted to the rotary shaft 
51 of the rotary cylinder 5 and the plate 23 is fixed on the upper surface 
of the cylinder flange 52 to complete assembly of the rotary cylinder 
power feeding apparatus. 
When the connecting terminals 24 and 25 are connected, the plate 23 of the 
rotary cylinder power feeding apparatus 7 will be in lose contact with the 
cylinder flange 52 of the rotary cylinder 5, and, when the plate and the 
shaft cap 22 are fitted to the rotary shaft 51 of the rotary cylinder 5, a 
predetermined contact pressure will be given and the contact will be able 
to be positively held. 
Thereby, the power from the body will be fed, as shown in FIG. 8, to the 
main substrate connector 30a through the main substrate 30 from the power 
source apparatus (not illustrated) provided, for example, on the main 
substrate 30. Power is then fed to the brushes 7a and 7b of the rotary 
cylinder power feeding apparatus 7 through the conductive member (not 
illustrated) within the arm 15 from the connecting terminals 15a and 15b 
of the arm 15 connected with this main substrate connector 30a. Then power 
is fed to the connecting terminals 24 and 25 extended into the rotary 
cylinder 5 through the commutators 7c and 7d contacting these brushes 7a 
and 7b while rotating and will be able to be fed to the electronic circuit 
of the preamplifier through the printed wiring (not illustrated) on the 
preamplifier substrate 26 from the preamplifier land 27 connected with the 
connecting terminals 24 and 25. 
When the electronic circuit of the preamplifier is driven by the power fed 
by the above mentioned rotary cylinder power feeding apparatus, at the 
time of the reproduction, the video signals detected from the magnetic 
heads 5a and 5b will be amplified and will be fed to the fixed cylinder 6 
side, that is, to the signal processing circuit (not illustrated) provided 
on the main base 30 through the magnetically connected rotary transformer 
56. 
Therefore, according to this embodiment, when power from the body is to be 
fed, for example, to the electronic circuit of the preamplifier within the 
rotating rotary cylinder, the main base substrate provided with the power 
source apparatus will be able to be connected to the preamplifier 
substrate on which the electronic circuit of the preamplifier within the 
rotary cylinder is arranged without using lead wires so that the rotary 
cylinder power feeding apparatus assembling work may be simplified. 
Because no lead wire is used in the connecting structure, problems with 
contacts between the lead wires entanglements with the rotary cylinder or 
breakage can be prevented. 
Further, because the brushes, commutators, shaft cap, plate and connecting 
terminals are integrated to form the rotary cylinder power feeding 
apparatus, assembly is easy and the number of the parts can be reduced and 
therefore it is evident that the cost can be also reduced. 
The rotary cylinder power feeding apparatus to which a countermeasure 
against noise is applied shall be explained in the following. 
FIGS. 10 to 15 illustrate the fourth embodiment of a rotary cylinder power 
feeding apparatus according to the present invention. FIG. 10 is a 
perspective view showing the formation of a commutator. FIG. 11 is a plan 
of a rotary cylinder power feeding apparatus using the commutator. FIG. 12 
is a side view of FIG. 11. 
The commutator shown in FIG. 10 comprises two conductors 72a and 72b but, 
as opposed to FIG. 4, the connecting terminals at the lower ends of the 
conductors are omitted. These two conductors 72a and 72b are obtained by 
dividing a cylindrical form into two parts. When assembled, these two 
conductors will be pasted on the outer peripheral surface of a commutator 
core 70 to be fitted on a rotary shaft 12. At this time, between the 
conductors 72a and 72b pasted around the commutator core 70, as shown in 
FIG. 11, two slits will be formed as joint parts. The center angle of the 
conductor 72a of the two conductors 72a and 72b arcuate in the 
cross-section is set to be an angle larger than the tape 40 winding angle 
(about 190 degrees) on the rotary cylinder 5. Here, the center angle of 
the conductor 72a is made about 270 degrees and the center angle of the 
conductor 72b is made about 90 degrees. The magnetic tape 40 is used as a 
tape-like, recording medium to record and reproduce an information signal, 
such as a video signal. 
As shown in FIG. 11, the magnetic tape 40 is wound on the rotary peripheral 
surface of the rotary cylinder 5 by using loading posts 41 and 42. 
Usually, the tape 40 is wound in a little excess of 180 degrees around the 
rotary cylinder 5. The angle connecting the two loading posts 41 and 42 
and the center of the rotary shaft 12 is about 5 degrees larger on the 
respective loading post sides than the line of 180 degrees to be about 190 
degrees. As shown in FIG. 12, the conductive brushes 7a and 7b are fixed 
to the supporting arm 15 and the commutators 7c and 7d fitted to the 
rotary shaft 12 rotate together with the rotary cylinder 5 and slide with 
the brushes 7a and 7b. Power is fed to the brushes 7a and 7b through the 
lead wires 29a and 29b from the power source apparatus arranged on the 
main substrate (not illustrated). The commutators 7c and 7d are connected 
with a relay lead 21a through the lead wires 13 and connector 21. The 
relay lead 21a is connected with the electronic circuit of the 
preamplifier of the preamplifier substrate 26. Therefore, the power source 
apparatus (not illustrated) is electrically connected to the electronic 
circuit within the rotary cylinder 5 through the brushes 7a and 7b. 
In this formation, because the commutators 7c and 7d comprise respectively 
two conductors 72a and 72b, slits as joint parts will be made between the 
conductors 72a and 72b and between the conductors 72b and 72a. 
Accordingly, when these slit parts contact the brushes 7a and 7b, the 
contact resistance will become unstable and an electric noise will be 
generated. The generated electric noise will be transmitted to an 
electronic circuit noise removing device mounted on the preamplifier 
substrate 26 through the lead wires 13, connector 21 and relay lead 21a, 
will generate electromagnetic waves around the noise removing device and 
will plunge into the nearby magnetic head 5a. However, in this embodiment, 
as shown in FIGS. 13 and 14, when the slit part of the commutator contacts 
the brushes 7a and 7b (when an electric noise is generated), the head 5a 
likely to be influenced by the electric noise will not contact the tape 40 
having recorded an information signal and will not detect the signal and 
therefore the head 5a will not be influenced by the electric noise. At 
this time, the head 5b hard to be influenced by the electric noise and on 
the side opposed by 180 degrees to the head 5a will be in contact with the 
tape 40 to detect the signal. As a result, no noise will be mixed in the 
signal obtained by synthesizing the respective signals detected by the 
heads 5a and 5b. 
FIGS. 13 and 14 are plan views showing the rotary cylinder power feeding 
apparatus when the brushes 7a and 7b contact the slit part of the 
commutator and an electric noise is generated depending on the rotating 
position of the rotary cylinder 5. FIG. 13 shows that the rotary cylinder 
5 rotates and the slit part between the conductors 72a and 72b forming the 
commutator is in contact with the conductive brushes 7a and 7b. At this 
time, the head 5a will not be contact with the tape 40 and will not detect 
the signal but the other head 5b hard to be influenced by the electric 
noise will be in contact with the head 5b and will detect the signal. 
Therefore, the electric noise generated at this time will not influence 
the signal detection of the heads 5a and 5b. When further rotated from 
this state, such electric noise as is shown in FIG. 15d will be generated 
by way of the contact state (See FIG. 11) of the conductor 72a larger in 
the center angle with the brushes 7a and 7b. FIG. 14 shows that the rotary 
cylinder 5 rotates from the state in FIG. 13 and the other slit part 
between the conductors 72b and 72a forming the commutator is in contact 
with the conductive brushes 7a and 7b. Also, at this time, the head 5a 
will not be in contact with the tape 40 and will not detect the signal but 
the other head 5b hard to be influenced by the electric noise will be in 
contact with the tape 40 and will detect the signal. Therefore, the 
electric noise generated at this time will not influence the signal 
detection of the heads 5a and 5b. 
FIG. 15 shows a phase relation diagram of the head detected signal, 
synthesized signal and electric noise generating position in the apparatus 
shown in FIGS. 11 to 14. In FIG. 15, (a) shows a head 5a detected signal, 
(b) shows a head 5b detected signal, (c) shows a synthesized signal of the 
detected signal of (a) and the detected signal of (b) obtained by 
switching the heads and (d) shows an electric noise generated by the slit 
part of the commutator comprising the conductors 72a and 72b. 
As the two slits of the commutator exist in a position which has passed a 
rotation angle of 270 degrees from the first slit and in a position which 
has further passed 90 degrees from that position, the electric noise shown 
in FIG. 15 (d) will be generated whenever the rotary cylinder 5 rotates by 
270 and 360 degrees from the first slit position. This is a position in 
which the head 5a has rotated by 225 degrees (shown in FIG. 14) and 315 
degrees (shown in FIG. 13) from the time point A at which the head 5a 
contacts the tape 40. In this position, the head 5a will be in a phase 
relation in which the head 5a will not contact the tape 40 (that is, will 
not detect the signal). On the contrary, in the phase relation in which 
the head 5a will contact the tape 40 (that is, will detect the signal), no 
electric noise will be generated and, as shown in FIG. 15 (a), no noise 
will be generated in the detected signal of the head 5a. Also, because the 
head 5b is on the side opposed by 180 degrees to the lead wires 13, 
connector 21 and relay lead 21a, as shown in FIG. 15(b), no noise will be 
generated in the detected signal of the head 5b. Therefore, as shown in 
FIG. 15c, no noise will be generated in the head synthesized signal 
obtained by switching the heads 5a and 5b. 
Thus, because the center angle of one of the conductors of the commutator 
combining a plurality of conductors is formed to be larger than the tape 
winding angle and the position of the slit part between the conductors, 
the connecting positions of the lead wires connected from the conductive 
brushes and commutators to the electronic circuit of the rotary cylinder 
and the position of the magnetic head are arranged to not influence the 
head synthesized signal used finally as an output. When the brushes 7a and 
7b contact the slits existing on the commutators 7c and 7d, 
electromagnetic waves will be generated around the lines electrically 
connected from the commutators 7c and 7d to the electronic circuits 
mounted on the preamplifier substrate 26, and even if the electromagnetic 
waves plunge into the head 5a nearby these lines, because the rotational 
phase of the head 5a is not detecting the signal of the tape 40, no noise 
will be generated in the head synthesized signal obtained as a result. 
Therefore, even if the commutator is formed of a plurality of conductors, 
the noise will be able to be prevented from influencing the head 
synthesized signal by the contact resistance. 
As described above, according to the present invention, the commutator 
assembly in the rotary cylinder power feeding apparatus can be made easy 
and the commutator can be simplified with respect to the rotary cylinder 
shaft and brushes with a simple formation. Further, without increasing the 
number of parts, the electronic circuit of the preamplifier can be 
connected and the rotating operation can be transmitted by the rotary 
cylinder. Also, the productivity can be improved without losing 
reliability and, at the same time, the power can be securely fed to the 
electronic circuit of the preamplifier. Further, a signal noise caused by 
the contact noise of the conductive brushes and the commutator formed of a 
plurality of conductors can be prevented from being generated. 
In the above described embodiments, the magnetic recording and reproducing 
apparatus wherein two magnetic heads are arranged as opposed to each other 
on the rotary surface of the rotary cylinder 5 has been explained. 
However, the present invention is not limited to this but can be applied 
to a magnetic recording and reproducing apparatus provided with one or 
more magnetic heads. 
Also, in the above described embodiments, the VTR has been explained as a 
magnetic recording and reproducing apparatus. However, the present 
invention is not limited to this but can be applied also to such apparatus 
for recording and reproducing information signals by means of a rotary 
cylinder as, for example, a digital audio tape recorder (DAT). 
The present invention is not limited to only the above described 
embodiments but can be variously modified without deviating from the 
subject matter of the invention, as defined in the appended claims.