GB508067A - Improvements in and relating to electric devices for operating hoists, cranes and the like - Google Patents

Abstract

508,067. Winches. TUSTIN, A., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. Dec. 21, 1937, No. 35409. [Class 78 (v)] An electric motor equipment for operating hoists, cranes, &c. comprises a main drumactuating motor and an auxiliary motor whereby sufficient power is applied to the drum to allow of manual control of the hook, &c., the drum and auxiliary motor then running independently of the main motor so that movement of the drum is not imparted to the main motor. The auxiliary motor may be coupled directly to the drum, or through gearing, the moment of inertia of the auxiliary motor, either direct or through gearing, being always such as to impose no undue resistance to manual movement of the hook. Fig. 1 shows a winding drum 1 fixed on a shaft 9 to which is directly coupled an auxiliary motor 3. A main motor 2 drives through a pinion 7 a gear wheel 8 loose on the shaft 9 but capable of imparting rotation thereto in the winding-on direction by pawls 13 engaging a ratchet wheel 12 fixed on the shaft 9.. Magnetic means may be provided for disengaging the pawls from the wheel 12 to free the motor 2 completely in both directions. This consists of a coil 16 surrounding the pawl cage 81, Fig. 4, and acting on a magnetic pawl 85 normally biassed by a spring 86 into engagement with the ratchet wheel 12 through an opening 89 in the inner run of the cage. The pawl 85 is pivoted to a block 84 fixed to this inner rim, so that when said pawl is released by de-energization of the coil 16 it drops into engagement with the wheel 12 and is forced thereby to turn the rim 81 through an angle which permits the remaining spring-pressed pawls 13 to pass through openings 83 in the run and to engage the teeth of the wheel 12 without danger of catching on to the tips thereof. When the magnetic pawl release is not employed, the main motor is driven in the non-lifting direction so rapidly that no manual action combined with separating movements of the boom end and load will overtake it. In a modified arrangement the main motor is geared to a toothed wheel loose on a shaft co-axial with, and connected by pawl and ratchet wheel to, the drum shaft, a friction clutch being provided between the loose wheel and its shaft. A ring coil arranged around part of this clutch releases same when electrified, but when de-energized allows springs to force the frictional faces of the clutch together.' In a third form the two motors and the drumare co-axially arranged and are connected together through an epicyclic gear disposed within the drum. The auxiliarymotor drives through a ratchet-wheel engaged by pawls controlled by a circumferential electric coil. The motors may be operated in a constant current circuit which may be supplied by a metadyne. Electro-magnetic brakes 18 may be provided on the main motor shaft 4. 19 is an exciter which energizes the main motor winding in a direction opposed to its motion when it rotates above a limiting speed, thus keeping the speed of the drum down to safe values in both directions.