| 摘要 |
920,705. Control of motors. GOULD & EBERHARDT Inc. May 22, 1959 [March 20, 1959], No. 17616/59. Class 38 (3). [Also in Groups XXII, XXIV and XXXV] A circuit for controlling a power driven member of say a machine tool comprises a valve T normally conductive having a grid 23 maintained at cathode potential by a resistor 28, but connectible to earth through a pair of contacts C1, D1 When the member reaches the limit of its travel, contact C1 carried on the member makes with insulated contact D1 cutting off the valve T1, de-energizing a relay 25a which disconnects the driving source viz. electric motor or hydraulic cylinder over contacts 27a. In a modification, a second pair of contacts 27b are connected to a second valve T2 which prevents conduction of this valve when T1 is conducting. Other contacts C2, D2 and 270b operate on the reverse motion of the cylinder to hold T1 non-conducting when T2 conducts. An additional pair of contacts may be provided to cut off the supply if the first pair of contacts fail to prevent motion of the machine. |
