Abstract:
A fully-automatic antenna driving device comprises a radio switch consisting of a push type switch which is on only during being pushed, a self-holding circuit for self-holding an excited condition by the turning on of the push type switch, and a further push type switch which is off only during being pushed, thereby preventing an antenna from being extended only by turning on an ignition switch.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a fully-automatic driving device for a power-driven antenna of a radio for use in a vehicle. 
     2. Description of the Prior Art 
     A system for automatically extending and retracting an antenna arranged on a vehicle body for a radio in a vehicle has been known as shown in FIG. 1. 
     With this arrangement, when an ignition switch 1 is turned on and a radio switch 2 of a lock type is then switched on, a current is supplied from a battery 3 through these switches 1 and 2 to a radio 4 to actuate it and simultaneously a current is supplied to an exciting coil 5a of a relay 5 in the same manner to close a normally opened contact 5b. At this moment, an antenna rod has been retracted and hence a limit switch 6 has been closed to the on state so that a driving current flows from the battery 3 between terminals 7a and 7c of a motor 7 through the switches 1 and 2, contact 5b and the limit switch 6 to extend the antenna rod. 
     When the antenna rod extends to a predetermined length, the limit switch 6 is opened or turned off to shut off the driving current for the motor 7 so as to stop the extension of the antenna rod. 
     With the radio 4 in the operative condition and the extended antenna rod, when the ignition switch 1 or the radio switch 2 is turned off, the current supply to the radio 4 and the exciting coil 5a of the relay 5 is shut off to turn off the radio 4 and simultaneously to close a normally closed contact 5c. At this moment, the antenna rod has extended and hence a limit switch 8 has been closed to an on state, so that the current flows from the battery 3 between terminals 7b and 7c of the motor 7 through the contact 5c and the switch 8 now to retract the antenna rod. 
     When the antenna rod has been retracted to a predetermined length and housed in the body, the limit switch 8 is opened to shut off the driving current for the motor 7 so as to stop the retraction of the antenna rod. 
     With the driving device of the prior art as described with reference to FIG. 1, the antenna rod is adapted to extend or retract automatically in response to the on and off of the ignition switch 1 and radio switch 2. With such a driving device, the ignition switch is often turned off to stop an engine without switching off the radio switch 2. In this case, the antenna rod will extend at the moment when the ignition switch is again turned on for starting the engine, because of the lock type radio switch 2 remaining in an on condition. If a driver is not aware of the extension of the antenna, there is a danger to a person near the antenna and a risk of a touch of the antenna with a shutter of a garage when a car is being driven into or out of the garage. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention to provide an improved fully-automatic driving device for a power-driven antenna, which eliminates all the disadvantages of the prior art by an improved construction that a radio switch is turned off without fail in response to the shutting off of an ignition switch and an antenna rod is thus not extended only by turning on the ignition switch. 
     The invention will be more fully understood by referring to the following detailed specification and claims taken in connection with the appended drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a circuit of a device of the prior art as mentioned above; and 
     FIG. 2 is a circuit of a device of one embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIG. 2 illustrating one embodiment of the invention, an antenna driving circuit comprises an ignition switch 1, a battery 3, a relay 5, a limit switch 6, a motor 7, a limit switch 8 and the like in the same manner as that in FIG. 1. 
     However, a radio switch 2 different from that in FIG. 1 consists of a relay 2a, a switch 2b for turning on a radio and a switch 2c for turning off the radio. The switch 2b is a push type switch which is on only while pushed or depressed and automatically turns off when it is released. On the other hand, the switch 2c is off only while pushed. 
     With this arrangement, when the ignition switch 1 is turned on and the radio switch 2b is pushed to turn on and thus turn on the radio, a current flows through the battery 3, the ignition switch 1, an exciting coil 2d of the relay 2a and the switch 2b to excite the relay 2a so as to close normally opened contacts 2e and 2f. The current is therefore supplied from the battery 3 through the ignition switch 1 and contact 2f to the radio 4 and relay 5 to operate the radio 4 and simultaneously extend an antenna rod in the same manner as in FIG. 1. 
     Once the relay 2a has been excited, even if the switch 2b is released to turn off, the current still flows through the battery 3, the ignition switch 1, the coil 2d, the contact 2e and the switch 2c to form a self-holding circuit for the relay 2a keeping it in an excited condition so as to maintain the contacts 2e and 2f closed. Accordingly, after the switch 2b has once been pushed to turn on, even if the switch 2b is turned off, the contact 2f will be kept closed to continue supplying the current to the radio 4 and the relay 5. 
     Under a condition that the radio 4 is being operated and the antenna rod has been extended, the switch 2c is pushed to turn off the radio, so that the exciting current is shut off to release the excited condition of the relay 2a so as to open the contacts 2e and 2f. As a result, the current supply to the radio 4 and the relay 5 is interrupted to make the radio 4 inoperative as that shown in FIG. 1 and simultaneously a current flows through a contact 5c and the limit switch 8 to the motor 7 to retract the antenna rod. 
     On the other hand, under the condition that the radio 4 is on and the antenna rod has been extended, the ignition switch 1 is turned off, so that the current flowing through the coil 2d is interrupted to release the self-holding circuit so as to open the contacts 2e and 2f, with the result that the current to the radio 4 and the relay 5 is interrupted. Therefore, the exciting coil 5a of the relay 5 is deenergized to close the contact 5c, so that a current flows through the contact 5c and the limit switch 8 to the motor 7 to retract the antenna rod. 
     From this condition, even if the ignition switch is turned on to start an engine, the switch 2b for the radio is never turned on unless the switch 2b is pushed, so that exciting current never flows through the relay 2a and therefore the contact 2f is kept open. As the result, current is never supplied to the radio 4 and relay 5, so that the radio is not operated and the antenna rod is not extended. 
     As can be seen from the above description, according to the invention even if an ignition switch is turned on to start an engine, an antenna rod is not extended unless a switch 2b is pushed to turn a radio on. In this case, therefore, there is no longer any risk of an extension of an antenna rod against a personnel near the antenna or a contact of the antenna with, for example, a shutter of a garage when a car is driven thereinto or out thereof. 
     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details can be made therein without departing from the spirit and scope of the invention.