Communications: radio wave antennas – Antennas – Rod type
Patent
1989-12-21
1992-10-13
Wimer, Michael C.
Communications: radio wave antennas
Antennas
Rod type
318265, 318266, H01Q 1100, H02P 3080
Patent
active
051554968
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a device for automatically expanding and contracting an antenna. More specifically, the invention relates to a device which is constructed relatively simply and compactly in a clutchless manner, which automatically expands and contracts the antenna smoothly, which protects the wire, which is constructed at a reduced cost, which is highly durable, and which, under abnormal conditions, prevents a motor for driving the expansion/contraction operation from being burned out.
BACKGROUND ART
Automatically expanding and contracting an antenna mounted on an automobile or any other vehicle involves expanding and contracting the antenna from inside the vehicle such as from inside the driver's room which, in practice, is very useful and has heretofore been widely employed. In automatically expanding and contracting the antenna, however, it is generally accepted practice to execute a clutch function when the antenna is fully expanded or is fully contracted to disconnect the drive force from the motor. So far, such a clutch mechanism has chiefly been incorporated in a portion of the rotary member such as a gear that drives the winding of the antenna expansion/contraction wire or that drives the operation wire. The clutch is put into operation when a rotational resistance (load) greater than a predetermined value is generated in such a portion.
Systems which do not employ clutch means have been disclosed in U.S. Pat. No. 4,153,825 and JP-AS No. 57-28962. In the mounted on a worm shaft that is driven by a motor being opposed thereto using a support ring, and a switch provided in a circuit for driving the motor in the forward direction or in the reverse direction is turned off by the operation member when an overload is exerted such as when the antenna is fully expanded or is fully contracted. If mentioned in detail, the worm and the operation member fastened to the worm are suppressed by a coil spring so as not to be thrusted in the axial direction in the load of the members at the back of the worm wheel when the antenna is expanded or contracted. When the antenna is fully expanded or is fully contracted, the operation is stopped after an overload is produced on the motor wheel. As the motor continues to rotate, therefore, the thrust that exceeds the suppressing force of the coil spring urges the worm such that an operation member is urged (one operation member is urged toward the coil spring interposed between the operation members at the time of forward rotation, and the other operation member is urged toward the coil spring at the time of reverse rotation), and whereby the switch is turned off to stop the motor.
In the latter system described in JP-AS No. 57-28962, on the other hand, a pair of circuit breakers are provided for a path that supplies electric power to turn in the forward direction the motor that drives a wire transfer mechanism which expands or contracts the antenna and for a path that supplies electric power to turn the motor in the reverse direction. When the antenna is fully expanded or is fully contracted, a heavy current flows into the power supply path through the circuit breaker; i.e., the power supply path is opened and the motor is stopped. The above circuit breakers are so coupled together that when a contact of one circuit breaker is opened, a reset button of the other circuit breaker is actuated. To realize such an operation, the two circuit breaker cases are coupled together as a unitary structure as shown in FIG. 2 of the above publication. A slidable reset button is provided between the breaker pieces that undergo thermal deformation when a heavy current flows in the cases, and a contact or a terminal of each of the drive power supply paths is provided on the breaker cases, so that the operation is repeated when the antenna is fully expanded or is fully contracted.
In the above-mentioned conventional systems, the clutch mechanism requires a considerably great clutch force; i.e., the clutch mechanism has a diameter which is so great as to
REFERENCES:
patent: 3143696 (1964-08-01), Harris
patent: 4153825 (1979-05-01), Flora
patent: 4190841 (1980-02-01), Harada
patent: 4864322 (1989-09-01), Yamamoto et al.
patent: 4875053 (1989-10-01), Harada
Brown Peter Toby
Nippon Antenna Company Limited
Wimer Michael C.
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