ETV (Elevating Transfer Vehicle) is the cornerstone of most multilevel systems; they are available in three variations:
This is one with a mast in each corner and the conveyor deck slung between them on chains, it is quite complex in design and is now only favoured for large 20ft plus pallet handling. They also allow the cargo to project above mast height so are useful where the roof height is restricting the pallet storage system.
This is a simplified design where the conveyor is carried on a cradle slung between two central uprights allowing a cable winch to provide the raising and lowering function.
The cost is generally less than a 4 post variant but the masts must be full height plus space for a beam between them so building height is a major consideration.
The machine is mounted on two rails in or on the floor.
This is essentially the same as the two post Elevating Transfer Vehicle but with a single running rail on the floor and a support rail mounted in building roof structure or built in to the storage system support structure.
The advantage of this Elevating Transfer Vehicle is that it has greater lateral (Sideways) stability so can operate to far greater heights we have built to 7 levels but there are some systems that are double that height.