GB869439A - Improved speedometer, tachometer, or like instrument for measuring the speed of an object - Google Patents

Abstract

869,439. Indicating particular speeds. GENERAL MOTORS CORPORATION. Oct. 16, 1959 [Nov. 7, 1958], No. 35078/59. Class 106 (3). A warning device for a speedometer or similar instrument comprises a casing 10, a member 30 rotated to indicate the speed being measured, two series of electrical contacts 42, 44, mounted on an insulator 40 and connected in pairs, a contact 49 fixed to the member 30 and arranged to engage the contacts 42 successively as the member 30 rotates and a manually-operable contact 120 connected to a warning device and rotatable to engage the contacts 44 successively and so set the speed at which the warning device operates. A shaft 26 rotates at a speed proportional to that being measured and carries a U-shaped permanent magnet 28. The member 30 surrounds the magnet 28 and is itself surrounded by a stationary field cup 36 made of material of high magnetic permeability. The member 30 is fixed to a spindle 32 to which the speedindicating pointer 22 is also attached and this shaft is biased by a helical spring 54 towards the zero position. A plastic plate 40 is attached to the casing and carries a printed circuit consisting of the series of contacts 42, 44, electrical connections 46 and a continuous outer contact 70 adjacent the series 44. A contact 120 is carried by an insulator 114 fixed to a disc 98 and is arranged to bridge any selected contact 44 and the continuous contact 70. The disc 98 is rotatable by means of a knurled knob 152 driving a shaft 94 through gearing and is urged into the selected angular positions by a spring 106, detents 110 on which snap into openings 112, Fig. 3, in the plastic plate 40. The contact 70 is connected to the warning device, which may be a lamp or a buzzer. Thus a warning is given at any one selected speed and this speed is indicated by numerals on a disc 134 viewed through a window 141.