https://www.plantautomation-technology.com/articles/palletis...
How these Palletisers Work?

The name “high-level palletizer” describes, the operation of the machine. A high level palletizer receives the product being palletized at an elevation or level considerably above the pallet. The pallet is fed into the palletizer from a magazine or accumulation station. As the pallet enters the palletizer it is raised and positioned under a bed or tray. The product moves onto the bed or tray and is organized into a single layer or tier of product. The pallet is below the level of the assembled tier and the entire layer of product is gently placed on the pallet. The equipment then begins organizing the second tier of product, modifying the arrangement of the cases to match the requirement of the pallet pattern.

“Low level palletizers” have the advantage of smaller footprints than high-level machines. A pallet in a low level machine is neither raised nor lowered and the tier or layer is formed at a level closer to the floor. Each layer is formed on a bed and then raised and lowered to transfer the load to the stationary pallet. The bed then returns to the starting position and the next layer is formed. After the pallet is completely loaded, it is discharged from the palletizer and another pallet is positioned and the process is repeated. Low-level palletizers normally move two and possibly three layers per minute onto a pallet.
http://apolloproject.ru/products/tradicionnyy-palletayzer-s-...