JPS5917008Y2 - plunger control circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a plunger control circuit that presses a pinch roller against a capstan.

Since the rotating magnetic head of a video tape recorder (hereinafter abbreviated as VTR) requires a relatively long time to reach a constant speed rotation state after starting rotation, the rotating magnetic head must be rotated when setting the pause mode.

However, in a VTR in which the capstan and the magnetic head are driven by a common motor, the pinch roller and the capstan must be separated when setting the pause mode.

Furthermore, when remotely controlling the pause mode, it is necessary to rely on electrical means to separate the pinch rollers.

Therefore, a plunger is used as a means to press the pinch roller, and the plunger is activated in conjunction with recording and playback operations, and is deactivated when the pause mode is set, and activated again when the pause mode is released. However, since the plunger requires a large current only to start operation, it is not possible to simply control the circuit that supplies a small current to the plunger in order to maintain the operation state when the pause mode is set. The pinch roller cannot be brought into pressure contact with the capstan.

Therefore, the present invention has been developed in view of the above points,
This paper specifically proposes a plunger control circuit configured to remotely control pause mode setting and release operations.

The present invention will be described below with reference to an illustrative embodiment.

The figure shows an example of an implementation circuit of the present invention, where the figure number is the plunger coil of the pinch roller pressure contact plunger, SW1 is the playback switch linked to the playback operation button, SW2 is the recording switch linked to the recording operation button, and SW3 is the playback switch linked to the playback operation button. is a pause switch on the VTR side that is linked to the pause operation button, SW4 is a pause switch for the remote control, Ql is the first switching transistor that supplies a large current to the plunger coil L when the plunger starts operating, and Q2 is a maintenance current when the plunger is operating. A second switching transistor, Q3, which cuts off the second switching transistor, Q3, is a third transistor, Q3, which controls the second switching transistor, Q2.
4 temporarily makes the first switching transistor Q1 conductive when the pause mode setting is canceled; and a fourth transistor Q5 temporarily makes the first switching transistor Q1 conductive when the recording or playback mode is set. C1 is the first charging capacitor that becomes charged when the recording or playback mode is set, and C2 is the second charging capacitor that becomes discharged when the pause mode is set and becomes charged when the pause mode is canceled. Charge/discharge capacitor, Dl, D2. D3 represents a backflow blocking diode, respectively.

The operation of the circuit of this embodiment will be explained below.

First, the first control circuit 1, which operates in conjunction with recording and reproducing operations, turns on the third transistor Q3 and the second switching transistor Q2 by closing the reproducing switch SW1 or the recording switch SW2. At the same time, a charging current is caused to flow through the first charging capacitor C1, and the fifth transistor Q5 and the first switching transistor Q1 are temporarily made conductive. A large current is temporarily supplied to the plunger coil L from the stabilized power supply to operate the plunger, and then, as charging of the first capacitor C1 is completed, the first switching transistor Q□ is made non-conductive, and the stabilized coil L is turned off. A maintenance current is supplied to the plunger coil L from a stabilized power supply with a low potential of 12V derived from a power supply circuit 3 to maintain the operating state of the plunger.

The second control circuit 2, which operates in conjunction with the pause operation,
When the pause switch SW3 or SW4 is closed, a discharge path is formed for the second charging/discharging capacitor C2, which is in a charged state when the playback switch SW1 or recording switch SW2 is closed, and the third transistor Q3 and the second switch are connected to each other. The sustaining current is cut off by making the switching transistor Q2 non-conducting.
Deactivates the plunger.

Furthermore, in conjunction with the pause release operation, the pause switch SW
3. When SW4 is opened, the second charging/discharging capacitor C2 is charged again, the fourth transistor Q4 and the first switching transistor Q1 are temporarily turned on, and a large current is supplied to the plunger coil L. The plunger is operated, and thereafter the plunger coil L
Supplies maintenance current to.

Furthermore, when exiting the playback mode or recording mode, the playback switch SW1, which is linked to the return of the playback lid or the recording button, is pressed.
As soon as the recording switch SW2 is opened, the third transistor Q3 and the second switching transistor Q2 become non-conductive and cut off the supply of sustaining current.

Therefore, according to the present invention, the plunger that presses the pinch roller against the capstan can be controlled by remote control, which is highly effective.

[Brief explanation of drawings]

The figure shows an example of a circuit for implementing the present invention. Explanation of main drawing numbers, 1...first control circuit, 2...second
control circuit, Ql... first switching transistor,
Q2...Second switching transistor, L...Plunger coil, SWl...Regeneration switch, SW2...
...Recording switch, SW3. SW4...pause switch.

Claims (1)

[Scope of utility model registration request] Between the drive current supply terminal and the ground, a normally open first switching means and a plunger coil for pressure welding the pinch roller;
In a plunger drive circuit which connects a normally closed second switching means in series and connects a sustaining current supply terminal to a connection point between the first switching means and the plunger coil, a recording mode or reproduction mode setting operation is performed. A first control circuit temporarily closes the first switching means in response to a pause mode setting operation during recording mode or playback mode setting, and opens the second switching means in response to a pause mode cancellation operation. A plunger control circuit comprising: a second control circuit that temporarily closes the first switching means at the same time as closing the second switching means.