Patent GB-803614-A (GB)
Title: Improvements in or relating to speed-responsive electrical switching devices
Inventor: HENDERSON CYRIL
IPC: H01H3/56
Filed: 1955-05-11
Abstract: 803,614. Magnetic switches. SMITH & SONS (ENGLAND), Ltd., S. May 10, 1956 [May 11, 1955], No. 13588/55. Class 38 (5). A switch for use in the automatic gear-change system of a motor vehicle and responsive both to the vehicle speed and also the throttle setting comprises a shaft 2 driven from the tail shaft of the gear-box and driving a hollow eddy-current rotor 17 receiving a cylindrical permanent magnet 30 rotatable about an arbor 27. A disc 32 fixed to the magnet 30 is biased counter-clockwise by a hairspring 31 and carries a column 33 supporting a contact unit 34. The unit 34 has a contact 35, a permanent magnet 36 and an arcing contact 37, and when the shaft 2 is rotating only slowly in the clockwise direction the bias of spring 31 holds the unit 34 against a contact unit 9 including a contact 12, a permanent magnet 13 and an arcing contact 14, whereby the contact pairs 35, 12 and 37, 14 are held closed, the attractive force between the magnets 36, 13 assisting the spring bias. A lever 38 pivotally mounted about an axis concentric with the shaft 2 is biased counterclockwise by an adjustable hair-spring 41 so that a contact unit 39 (similar to the unit 34) on the lever engages a contact unit 10 (similar to unit 9). The unit 10 (Fig. 6, not shown), is spaced clockwise relatively to the unit 9 so that as the speed of shaft 2 increases the unit 34 first leaves unit 9 to bring about a change from first to second gear, and then if the speed further increases an upstanding arm 50 of the unit 34 engages a depending arm 49 of the lever 38 to disengage the units 39, 10 and effect a change from second to third gear. A further lever 51 (similar to lever 38) is biased in the counterclockwise direction by an adjustable hairspring 54 so that a contact unit 52 (similar to unit 34) thereon engages a contact unit 11 (similar to unit 9). The unit 11 (Fig. 6, not shown) is spaced clockwise relatively to the unit 10 so that as the vehicle speed-still further increases an upstanding arm 48 of the lever 38 engages a depending arm 61 of the lever 51 to disengage the units 52, 11 and effect a change from third to fourth gear. On a decrease in vehicle speed the pairs of contact units re-engage successively but at lower speeds than those at which they were disengaged owing to the effect of their permanent magnets. The units 9, 10, 11 are carried, respectively, by the lower ends of three posts (Figs. 5, 6, not shown) depending from a moulding 5 fixed to a stub shaft 4, the posts being spaced apart and equidistant from the shaft axis. The shaft 4 is adjustable by an arm (Fig. 1, not shown) connected to the throttle, opening of the throttle causing clockwise rotation of the shaft so that higher vehicle speeds are necessary to effect the various gear changes by the shaft 2. To prevent a change from fourth to third gear with a too high vehicle speed a non-spring-biased lever 65 carries a contact 67 and permanent magnet (not shown) co-operating, respectively, with a fixed contact 63 and permanent magnet (not shown) of a member 62 attached to switch housing 1. The arrangement is such that at a certain speed the magnet 36 of unit 34 engages a magnetic depending arm 68 of the lever 65 to disengage the contacts 67, 63 and the lever 65 is thus carried by the magnet 36 until the speed falls sufficiently for the contacts to re-engage. In a different construction described in the Provisional Specification with reference to drawings (not shown) a double-ended contact moves between a pair of adjustable contacts in dependence upon the vehicle speed, the doubleended contact engaging one adjustable contact in the bottom gear position and leaving this adjustable contact to obtain the intermediate gear, the top gear being obtained when the double-ended contact engages the other adjustable contact. The adjustable contacts are movable in dependence upon the throttle setting through an epicyclic gear.