Automatic recording level control device for magnetic tape recorder

Claim 2

A recording level automatic control device for magnetic tape recorders comprising a recording circuit including a variable resistor for regulating the recording level, a driving means for varying the variable resistor of said recording circuit, a rectifying circuit for producing a DC signal proportional to the average value of the recording current in the recording circuit, a detecting circuit responsive to said DC signal for producing an output signal indicating that the recording current of said recording circuit has become adapted for an appropriate recording, and a stop means responsive to said output signal for stopping said driving means to thereby stop the change of the variable resistor.

Claim 3

A recording level automatic control device as claimed in claim 1, wherein said rectifying circuit is adapted to rectify the recording current flowing into the variable resistor of said recording circuit, and said detecting circuit is constituted by a bridge circuit, one resistor element of said bridge circuit being consisted of another variable resistor adapted to change by means of said driving means in synchronism with the variable resistor of said recording circuit.

Claim 4

A recording level automatic control device as claimed in claim 1 wherein said rectifying circuit comprises a Zener diode at the output side, said DC signal beiNg applied to said detecting circuit when the voltage applied to said Zener diode exceeds the Zener voltage.

Claim 5

A recording level automatic control device as claimed in claim 1, wherein said driving means is comprised of a gear train and a source for driving the gear train, one rotating shaft of said gear train being connected to the operating shaft of the variable resistor of said recording circuit.

Claim 6

A recording level automatic control device as claimed in claim 4, wherein said stop means comprises an electromagnetic plunger operable in response to the output of said detecting circuit, and a friction wheel provided on one of the gears of said gear train and disposed against said electromagnetic plunger, the rotation of gear train being stopped by engagement of the actuator of the electromagnetic plunger with the friction wheel when the electromagnetic plunger is not operated.

Claim 7

A recording level automatic control device as claimed in claim 5, wherein the rotating and driving source of said driving means comprises a manually slidable rack, and a pinion gear engaged with said rack and connected with said gear train, the variable resistor being changed in a direction in which the recording level of said recording circuit is increased by pushing of the rack, whereby a fade-in recording is made possible.

Claim 8

A recording level automatic control device as claimed in claim 5, wherein the rotating and driving source of said driving means comprises a rotating shaft provided with one gear of the gear train of said driving means, a spring energized by manual rotation of said rotating shaft, and a lever member stopping the rotation of the rotating shaft against the elastic force of said spring, the rotating shaft being rotated by the restoring force of the spring by releasing the rotating engagement of the rotating shaft through manual operation of the lever member.

Claim 9

A recording level automatic control device as claimed in claim 7, wherein the variable resistor is provided on the same rotating shaft of said rotating and driving source, the variable resistor being adapted to be set at zero by the rotation of the rotating shaft when energizing said spring, the variable resistor being adapted to change in a direction to increase the recording level of said recording circuit at the control of recording level, whereby a fade-in recording is made possible.

Claim 10

A recording level automatic control device for magnetic tape recorders comprising a recording circuit including a variable resistor for regulating the recording level, a driving means for varying the variable resistor of said recording circuit including a gear train, one rotating shaft of said gear train being connected to the operating shaft of the variable resistor of said recording circuit, a rectifying circuit for producing a DC signal proportional to the average value of the recording current in the recording circuit, a detecting circuit responsive to said DC signal for producing an output signal indicating that the recording current of said recording circuit has become adapted for an appropriate recording, and a stop means responsive to said output signal for stopping said driving means to thereby stop the change of the variable resistor, and wherein said stop means comprises an electromagnetic device provided with a coil to which the output current of said detecting circuit is applied, and a magnetic piece adapted to be magnetically attracted to said electromagnetic device; a rotating and driving source for said gear train comprising a capstan for running and driving the magnetic tape, and a frictional rubber wheel adapted to rotate in abutment with said capstan; said frictional rubber wheel and said gear train being connected with each other and each being mounted on a rotatably supported swing lever, a spring provided on said swing lever to keep the frictional rubber wheel away from the capstan, the swing lever being adapted to be rotated against the bias of said spring by the magnetic attraction of said magnetic piece by the electromagnetic device so that the pressing contact between the capstan and the frictional rubber wheel is obtained and the variable resistor is changed and the swing lever is adapted to be restored by the bias of said spring when there is no magnetic attraction between the electromagnetic device and the magnetic piece, said electromagnetic device being responsive to the output of said detecting circuit to release said magnetic attraction, whereby the change of the variable resistor is stopped.

Claim 11

A recording level automatic control device for magnetic tape recorders comprising a recording circuit including a variable resistor for regulating the recording level, a driving means for varying the variable resistor of said recording circuit including a gear train, one rotating shaft of said gear train being connected to the operating shaft of the variable resistor of said recording circuit, a rectifying circuit for producing a DC signal proportional to the average value of the recording current in the recording circuit, a detecting circuit responsive to said DC signal for producing an output signal indicating that the recording current of said recording circuit has become adapted for an appropriate recording, and a stop means responsive to said output signal for stopping said driving means to thereby stop the change of the variable resistor, and wherein said stop means comprises an electromagnetic device provided with a coil to which the output current of said detecting circuit is applied, and a magnetic piece adapted to be magnetically attracted to said electromagnetic device; a rotating and driving source for said gear train comprising a capstan for running and driving the magnetic tape, and a frictional rubber wheel adapted to rotate in abutment with said capstan; said frictional rubber wheel and said gear train being connected with each other and each being mounted on a rotatably supported swing lever, a spring provided on said swing lever to keep the frictional rubber wheel away from the capstan, the swing lever being adapted to be rotated against the bias of said spring by the magnetic attraction of said magnetic piece by the electromagnetic device so that the pressing contact between the capstan and the frictional rubber wheel is obtained and the variable resistor is changed and the swing lever is adapted to be restored by the bias of said spring when there is no magnetic attraction between the electromagnetic device and the magnetic piece, said electromagnetic device being responsive to the output of said detecting circuit to release said magnetic attraction, whereby the change of the variable resistor is stopped.

Claim 12

A recording level automatic control device as claimed in claim 9, wherein the electromagnetic device of said stop means is comprised of a first coil through which a weak current normally flows, a second coil through which a current is caused to flow in response to the output of said detecting circuit, and a core wound with the first and the second coils having magnetically open ends, and a lever member is provided for swinging and operating said swing lever against the bias of the spring, said magnetic piece being arranged to close the magnetically open ends of said core by the swinging of the swing lever operated by said lever member and to be attracted and held on the core by a magnetic flux produced by said first coil, said coils being so arranged that the magnetic flux of the first coil is cancelled by the magnetic flux produced by said second coil, whereby the attraction of the core and the magnetic piece is released.

Claim 13

A recording level automatic control device as claimed in claim 9, wherein the magnetic piece of said stop means is made of a permanent magnet, and said electromagnetic device is comprised of soft steel plates and a coil wound on said steel plate in such a manner that current flowing in said coil cancels the magnetic flux of the permanent magnet to eliminate the attractive force between the permanent magnet and the soft steel plates.

Claim 14

A recording level automatic control device as claimed in claim 9, wherein a knob is provided on a shaft of said gear train, said knob being adapted to be operated manually when the capstan and the frictional rubber wheel are not pressed and contacted, whereby when the variable resistor is set at zero prior to the automatic control of the recording level fade-in recording is made possible.

Claim 15

A recording level automatic control device as claimed in claim 9, wherein the magnetic piece of said stop means is provided on the swing lever through a spring plate, said swing lever being biased by said spring plate to exert a pressing and contacting force between the capstan and the frictional rubber wheel.