GB1398105A - Hoist - Google Patents

Abstract

1398105 Hoists ATLAS COPCO AB 6 Sept 1972 [9 Sept 1971] 41254/72 Heading B8B A reversible motor driven hoist includes a mechanism responsive to a tendency of loaddriven turning of the drum 24 to force drum braking means into a braking position when the motor 21 is stopped and an elastically yieldable means associated with the mechanism for limiting the operating force applied to the braking means to limit the braking force. The motor 21 which may be pneumatic or electric has an output shaft 22 to drive the drum 24 through transmission gear and to the end of which a brake disc 43 is rotatably secured and axially positioned between brake shoes 66 on a carrier 64 and brake shoes 47 on a carrier 46, a weak spring 63 biasing the shoes and discs into slipping contact in the released condition of the brake. The brake shoe carrier 46 is centrally carried on an adjusting screw 50 which also carries an inner cross member 52 rotatably securing the carrier 46 to a plate 55 swinging from the hoist housing 20 at screw 72, and an outer cross member 53 rotatably secured to the plate 55 by pins 56. Thrust rods 61 extend obliquely between the inner and outer cross members so that relative rotation of the two cross members causes the inner member 52 to move axially away from the cross member 53 to thereby apply the disc brake 46, 43, 64. In operation, when a load is to be lifted a pivoted yoke 36 under the hoist housing 20 is appropriately tilted by depending ropes 39, which turns a control shaft 34 to operate the motor 21 in a lift direction, the brake slipping as the load is lifted. Upon stopping the motor, the load tends to lower but rotation of the brake disc 43 in this direction causse the thrust rods 61 to become more axial and apply the brake harder, the amount of brake force being restricted by a spring 74 biasing the swinging plate 55 in the braking direction. When the load is to be lowered, the shaft 34 is turned to reverse the motor 21 and a cam block 80 on the shaft causes the plate 55 to be pushed against the bias of the spring 74 to prevent application of the brake. The yoke 36 is engageable by the load hook or load at the limit of its lift, to rotate the control shaft 34 into the motor neutral position to prevent further hoisting. In the embodiment of Figs. 11, 12 and 13 (not shown) the brake is released during load lowering by a pneumatic diaphragm arrangement, the supply of air thereto being controlled by the control rod when the motor direction is selected. The brake disc and shoes are forced into interengagement when the load tends to lower under its own weight by a cam and follower arrangement associated with the brake disc.