Layer Palletizer

Overview

A layer palletizer builds an entire pallet layer flat, then deposits it onto the stack in one motion, rather than placing cases one at a time the way a robot does. This is the older and faster of the two palletizing approaches: where a single robot arm tops out around a thousand cases an hour, a layer machine handles up to two hundred cases a minute because it moves a whole layer at once. The tradeoff is flexibility. A layer palletizer is mechanical tooling tuned to a range of case sizes, so it suits high-volume lines running few SKUs, such as beverage, canned goods, and bagged product.

How it works

Cases enter on the Infeed Conveyor conveyor in single file from the packing line. A Case Orienter turns selected cases ninety degrees so the layer pattern interlocks like brickwork, which is what gives the finished stack its stability. The cases then accumulate in the Row Former, a low-back-pressure conveyor where a retracting Row Stop counts and holds them until a full row is queued and squared against side guides. A servo Row Pusher slides the finished row sideways onto the Layer Table.

Rows accumulate on the layer table until a full pallet layer is assembled against the Back Fence. Pneumatic Layer Tamper plates close in to tighten the layer so there are no gaps. The transfer is the clever part: the layer sits on a retracting Apron Plate, a sliding deck. A Sweep Transfer bar moves out to hold the layer in place, and the apron withdraws from under it, so the whole layer lowers onto the pallet without being dropped or pushed. The Pallet Elevator then lowers the pallet by exactly one layer height so the next layer deposits at the same fixed level, and the cycle repeats until the stack is complete.

Pallet handling

The machine supplies and removes pallets itself. An integral Pallet Magazine holds a stack of empty pallets, supports all but the lowest on retracting pawls, and feeds one onto the Pallet Conveyor when the elevator calls for it. The elevator's forked Lift Table raises that empty pallet to the deposit height, then steps down layer by layer as the stack grows. When the pallet is full it lowers to floor level and a Discharge Conveyor carries it out to a stretch wrapper or shipping. Because pallet supply and discharge are built in, the machine runs without an operator between magazine refills.

Materials and construction

A layer palletizer is a heavy steel machine because it moves layers that can weigh several hundred kilograms many times a minute. The Frame & Guarding is a welded steel weldment that holds the row former, layer table, sweep, and elevator on a common datum, since layer formation depends on every station staying square to the others. The apron slats and sweep bar are faced to slide without marking cases, and conveyor rollers are steel tube on internal bearings. The elevator runs on a forked lift table guided by columns and hoisted on roller Lift Chain driven through a worm gearbox, which holds position when power is removed. Perimeter guarding is interlocked sheet metal; opening the Access Gate drops the safety circuit and stops all motion.

Control and patterns

The Control Cabinet cabinet holds a PLC, one Servo Drive per major axis, and the operator Operator HMI. The PLC sequences the orienter, row stop, pusher, tamper, sweep, and elevator against each other so timing never lets a case escape or a layer drop early. Layer patterns are stored as recipes: an operator selects the product and the machine sets the orientations, row counts, and layer count for that case size. Switching products is a recipe change plus a quick guide-rail adjustment rather than a tooling rebuild, though the range of case sizes a given machine handles is fixed by its mechanical layout.

Variants and use

Layer palletizers split into high-infeed and low-infeed types. High-infeed machines, like the one described here, bring cases in above the stack and drop layers down onto a descending pallet; low-infeed machines bring cases in at floor level and raise the layer, which suits sites with limited overhead height. Beverage lines often add a tier-sheet placer between layers for stability, and high-rate plants run two row formers feeding one layer table to keep up with fast fillers. In service the machine is largely unattended, with maintenance focused on the sweep and apron slides, the elevator chains, and the pneumatic tampers and stops. The recurring consumable is wear strips on the case-contact surfaces, replaced before they begin to mark product.