GB1355041A - Vehicle station keeping device - Google Patents

Abstract

1355041 Indicating safe vehicle distance NATIONAL RESEARCH DEVELOPMENT CORP 19 April 1971 [24 Feb 1970] 8875/70 Heading G2J [Also in Divisions G1 and G4] The speed of a motor car is measured electrically and used to control the distance between two vertical lines on e.g. the windscreen, so that the driver knows that by keeping his view of a preceding car between these lines he is following at a distance consistent with his speed and braking distance. As shown Fig. 1, a flexible cable 3 from a wheel shaft drives a tachogenerator 1 to produce a D.C. voltage which is amplified at 5 to energize a servomotor 6. The latter drives a lead screw 11 carrying a feedback potentiometer 13 for amplifier 5, and two lamp boxes 12, 12' on left and right hand threads, whereby rotation of shaft 11 due to an increase in road speed brings the boxes closer together and vice versa. The boxes contain lamps which shine through graticules 14, 14' and the two lines are fed through a collimating optical system to appear on an adjustable combing screen 16. The dimensions are such that for cars of an average 5 feet width, the separation between cars is 15 feet per 10 mph road speed. The servomotor 6 may be continuously variable or respond to unit change of speed e.g. 5 mph. The tachogenerator output may be fed through a switching device 43 Fig. 3 to selectively illuminate pairs of lamps 41 from the outside of a matrix 40 inwards as the car speed increases. In another embodiment Fig. 2 the drive cable 21 drives a speedometer drag-cup movement 22 carrying a biasing hairspring 25 and a drum 24 with two circumferential convergent lines 26 milled through it. Light from a lamp 27 is reflected by a prism 28 through the lines 26 to form the desired spaced parallel lines on a combining screen 32. (For Figures see next page)