Manual chain hoist is a kind of light and small manual lifting machine with simple structure and wide application range. There are two kinds of hand hoist: hand chain block and lever hoist. Manual hoist is a kind of lifting machinery, which is characterized by unidirectional load all the time. Therefore, its brake mechanism usually adopts spiral load self-made brake, which automatically generates braking moment in the brake by using gravity or traction of the weight itself. This kind of brake is characterized by simple structure, compactness, automatic braking and no additional force. The braking performance of the brake is directly related to the size of screw, brake parts and friction pads. The influence of these factors should be considered comprehensively in the design.
The manual hoist brake mechanism consists of three parts:
1. Spiral - Thread between the long shaft and the hand sprocket (brake nut).
2. Disc brake - hand sprocket (brake nut), friction disc, ratchet and brake seat;
3. The ratchet stopper, ratchet wheel and ratchet pawl, is to illustrate the working principle of manual hoist brake mechanism by lifting weights.
When lifting heavy objects, pull the hand zipper (or pull the handle), and the hand sprocket 6 (brake nut 8) rotates from the thread to the friction disc 5, so that the friction disc, ratchet wheel 2 and brake seat 3 are pressed together and rotated as a rigid connection. At this time, the pawl 1 slides over the ratchet 2 teeth, and the brake mechanism acts as a coupling. Once the operation is stopped, the long axis will be dragged to reverse at noon, but the ratchet wheel 2 is jammed by the ratchet claw 1, and the mechanism is in braking state, so that the weight will stop. When the weight is lowered, pull the hand zipper 7 (or pull the handle 9) backwardly. As the hand sprocket 6 (brake nut 8) rotates slightly in reverse, the axial pressure between the friction discs decreases, the braking moment decreases, and the friction disc 5 slips. At this time, the ratchet 1 throws the ratchet 2 and the ratchet 2 does not move and slowly falls at noon. Once the pull stops. The heavy material desire drags the long axle down continuously. The brake seat 3 is threaded to the friction disc 5. The friction disc 5, ratchet wheel 2, hand sprocket 6 (brake nut 8) and brake seat 3 are pressed into one again. The brake mechanism is jammed by the ratchet 1, and the brake mechanism enters the braking state again, so that it stops at noon. Such repetition can complete the lifting operation of heavy objects.