GB811388A - Overload protected electric motor drive - Google Patents

Abstract

811,388. Motor driving arrangements. DEAN, P. P. Sept. 17, 1956, No. 28320/56. Class 35. [Also in Groups XXIV and XXXVII] An overload protected electric motor drive comprises a motor rotor 4 which drives a hollow drive shaft 12 to which is connected for rotation but is axially slidable relatively thereto a worm 34 carried by an inner shaft 30 extending through the drive shaft 12, and a spring 40 disposed inside the drive shaft 12 and outside the inner shaft 30 and yieldably maintaining the shafts in predetermined axial relation, the energization of the motor being interruptable by a switch actuated upon axial sliding of the worm in response to axial thrust on the worm in excess of the force of the spring when the drive is overloaded. As shown, two switches 68, 72 are provided, both serially connected in the motor energization circuit, and have arms 70, 74 operable by a disc 62 adjustably positioned on an inner shaft extension 60 to open the motor circuit upon the inner shaft moving respectively to the left or right when a wormwheel 36 driven by the worm 34 in a clockwise or counterclockwise direction encounters, e.g. an obstruction. The switches may also control a visual or audible alarm signal; they may be self-locking, requiring to be reset when opened, or alternatively the worm and worm-wheel teeth may be non-reversible to hold the switches open until the overload is removed. The rotor shaft 12 is mounted in ball-bearings 16, 18 carried in a tubular support 14 formed in the wall of a supporting housing 8.