GB1481928A - Extendible and retractable antenna - Google Patents

Abstract

1481928 Vehicle antenna NEW-TRONICS CORP 23 April 1975 16913/75 Heading H4A An extendible and retractable vehicle antenna comprises a rod 14, a track 30 mountable beneath and parallel with a vehicle panel 12, a rider 32 reciprocable along said track with means 56 on the rider for pivotally receiving the inner end of rod 14, antenna rod guide means 26, e.g. a ball, mountable on the panel 12 and rotatable about an axis perpendicular to a diametrical bore (86, Fig. 3, not shown) provided for the rod 14, and a bracket assembly 36, 38 for mounting the track 30 beneath panel 12. As described rider 32 is internally screw threaded to co-operate with a threaded shaft 66 within track 30, said shaft being driven by a reversible motor 64. Mounting plate 36 is connected with bracket 38 by a pivot pin 46 and a nut and bolt 50 in an arcuate groove 48 so that the track, mounted on said plate 36, can be set up vertically beneath the guide means 16 so that the antenna, when extended, is vertical. A conductive spring 60, having a channel 62 for the fully extended antenna, conducts the received signals through an inductor 61 to the receiver. The inductance 61 is so chosen that the combination of antenna and inductance resonates at the centre of the received band (stated to be 98À0 MHz for f.m. reception). The guide means 16 comprises a spherical ball (Fig. 3) preferably of nylon, having a diametrical bore to slidably receive the antenna, the ball being retained in a part-spherical recess between two nylon plates (Figs. 3-5) which are secured to the vehicle panel. In an alternative embodiment (Figs. 6, 7, not shown) the motor is unidirectional and the shaft is reverse threaded so that the rider may travel in either direction during one direction of rotation of the shaft. The rider of this embodiment is therefore provided with a follower (138) to engage the threads of the shaft, the follower being mounted on a pin (140, Fig. 7) which may rotate in a recess (142) in the rider. In both embodiments the rider has two grooves which receive the edges of respective tracks 30, and prevent rotation of the rider. It is also possible to eliminate the motor and threaded shaft and extend and retract the aerial manually. Alternatively the rider could be driven by a pulley and chain. Switches 84, operable by the rider 32, are provided to switch off the motor 64 when the antenna is fully extended or retracted, there being a two-position switch within the driver's compartment to start the motor in either direction. In the second embodiment the motor is operated by momentary depression of a push switch which is biased open by a spring. A circuit is described which maintains the operation of the motor after release of the switch until the rider opens a switch at one end of the track.