Differential Hoists use a loop of chain and a dual chain-wheel at the top with various number of pockets on the sides. The lower “hook” wheel has grooves to ride on the chain, but no pockets. As the chain is pulled around the inner load loop gets smaller or larger by the difference in the number of pockets on the chain-wheel (the differential). As the lifting loop gets shorter the hand loop gets longer and vice versa. This is a bit of an inconvenience but the mechanism is as simple as they get.
Lever Ratchet Hoists are small portable units with capacities up to 5 tons but the common ones are rated 1/2 or 1 ton. The ratchet handle operates simple gears that pull a short load chain. The load is supported by a disk type friction brake that looks like an automotive clutch disk held by a paw and sprocket (ratchet). Lifting rotates the brake/clutch on the ratchet. Lowering releases the pressure on the brake via a multi-lead screw similar to a brake Bendix.
Hand Chain Hoists operate like the ratchet hoists above, except a chain wheel and loop of hand chain turns the gearing. A brake holds the load and a ratchet prevents the brake from rotating one direction. The chain-wheel rides on a screw that loosens the brake when the chain is pulled in the lowering direction. Most have planetary gearing on the brake wheel. Chain hoists are made with straight pulls and compound pulls up to 10 tons or more, and are made in steel, portable aluminium housings, spark proof materials and corrosion resistant materials.