In essence, true vertical lift is a hoists ability to lift the hook straight up and down, to pick up or put down a load in an exact position with no hook drift. It occurs when a hoist (lower block) moves in a true vertical path between the lower limit of travel, which happens when the rope(s) anchored at each end of the drum wind from the centre of the drum outward (inward when raising the hook); enabling the hook and load to be centred below the middle of the drum. This design prevents the hook from wandering from one end of the drum to the other in the highest and lowest hook positions.
When a high degree of accuracy is required to pick or place a load, precise lifting is required and this only facilitated through true vertical lift. This need for precision and accuracy is often a requirement in manufacturing operations, injection moulding or speciality applications for the pharmaceutical industry.
It’s difficult to achieve true vertical lift with a single reeved wire rope hoist because the long, thin drum design means that the hook has greater horizontal movement allowed by the drums design and reeving during winding (raising and lowering). In a single reeved wire rope hoist there generally is a degree of hook drift expected, which is normal and acceptable for the majority of lifting and handling operations. Where there is a need for precision and accuracy a double reeved wire rope hoist, like the Eurobloc VT Electric Wire Rope Hoist (excluding VT1) would be required.
The standard reeving configuration for a wire rope hoist offering true vertical lift would be ‘two-part double’ reeving which involves four separate parts of wire rope, and it is also common for ‘four-part double’ reeving involving eight separate parts of wire rope to be used. A double reeved wire rope hoist is configured with wire rope that is fed through a series of sheaves in the hook block and hook frame, as well as being wound on the left-handed and right-handed grooving of the drum.
Using more parts of wire rope in the reeving configuration allows for greater precision when lifting and handling heavier loads at slower speeds. Where there is a need for precision and accuracy a double reeved wire rope hoist, like the Eurobloc VT Electric Wire Rope Hoist (excluding VT1) would be required.