GB970398A - Improvements in or relating to device for indicating a change of speed above a certain magnitude - Google Patents

Abstract

970,398. Differential switches. H. LEMONNIER. Aug. 1, 1961, No. 27787/61. Heading H2B. [Also in Division G1] Apparatus for indicating the slowing-down of a machine below a critical speed comprises (a) a slipping coupling driven by the machine and rotating a switch operating lever 3 and (b) a synchronous motor 10 rotating a contactor unit 13 at the critical speed about the same axis of rotation as the lever 3 for co-operation therewith. While the shaft 1 is rotating above the critical speed slipping of the coupling 2 will allow the unit 13 to hold down the speed of rotation of the lever 3 to the critical speed and the reaction between the lever 3 and unit 13 will hold the contacts 16, 18 closed, Fig. 4. If the machine slows down delow the critical speed the unit 13 will drive the lever 3 and the contacts 16, 18 will open to initiate a signal indicating slowing-down of the machine. In order to signal failure of the motor 10 a further slipping coupling 4 is driven from the driving member of the coupling 2 through reduction gearing and its driven member carries a switch-operating lever 5 for co-operation with another contactor unit 14 carried round with the unit 13. If the machine normally drives the shaft say, a 100 r.p.m. and 90 r.p.m. is fixed as the critical minimum speed then suitable reduction gearing would drive the driving member 4a at 80 r.p.m. while the motor 10 maintains a speed of 90 r.p.m. the contacts of unit 14 are closed, should it fall below 80 r.p.m. the contacts open and initiate a signal.