Horizontal Carousel

Overview

A horizontal carousel is a goods-to-person storage machine: instead of an operator walking aisles to reach stock, the stock travels to the operator. A closed train of shelved Bin Carrier columns hangs from an oval Track System and circulates on command, stopping with the requested bin column centred in a fixed pick window. The operator never moves; the Carousel Controller computes the shorter rotation direction for each request and pre-positions the next pick while the current one is being handled.

A typical unit carries 40 carriers, each rated up to 680 kg with eight adjustable Carrier Shelf levels, on a track 10–30 m long. Carousels are deployed in pods of two to four with one operator, so that one unit is always rotating while another presents a pick, this overlapping is what pushes pick rates to 200–400 order lines per hour per person, three to four times a walk-and-pick rate. Common applications are small-parts order fulfilment, spare-parts cribs and work-in-process buffering.

How it works

The Carrier Train is a chain of carriers joined by pivoting Carrier Link connectors, each carrier hanging from a two-wheel Carrier Trolley on the Top Rail Section and steadied at floor level by a Bottom Guide Shoe shoe in the Bottom Guide Channel. The links articulate around the machined End Curve Section sections at each end of the oval, so the train behaves as a single flexible loop.

The Drive Unit propels the train through a rubber-faced Traction Drive Wheel pressed against it by a spring Drive Tension Unit, driven by a 1.1–2.2 kW motor through a Drive Inverter. The inverter matters: a loaded train can carry over 20 t of stock, and acceleration must be gentle enough that open bins do not spill. Position is tracked by an encoder on the drive plus Carrier Position Sensor flags on each carrier, giving the controller absolute knowledge of which carrier faces the window. Rotation is bidirectional, so the worst-case move is half the track length; mean positioning time on a 40-carrier unit is a few seconds.

Pick station and software

Orders arrive over the WMS Gateway from the warehouse management system. The controller batches them: it sequences the pick queue to minimise total rotation, and in batch-pick mode the operator picks one SKU for several orders at once, distributing items into the lighted Batch Put Rack positions behind the station.

At the window, a Pick Light Tree LED column indicates the target shelf level and displays the quantity, the Barcode Scanner verifies the SKU, and the operator hits the Pick Confirm Button to release the next rotation. This pick-to-light loop removes paper and most picking errors; accuracy above 99.9 % is normal. Because the operator's hands stay at the Work Counter between waist and shoulder height, the ergonomics also beat shelving, where the same SKUs would span floor to overhead.

Structure and safety

The whole stored load hangs: the Support Frame uprights and Header Beam members carry the rail and the full train weight into the floor anchors, with Cross Brace diagonals taking drive and seismic loads. This top-hung arrangement keeps the floor under the train clear, which is why the bottom channel can be a simple guide rather than a load path.

Safety follows ANSI MH28.2. The moving train is fenced by Perimeter Guard mesh on all sides except the pick window, which is supervised by a Pick Window Light Curtain that stops rotation if anything crosses the plane while the train is moving. Service doors carry Access Door Interlock switches that drop drive power, and latching Emergency Stop buttons sit at the station and rear.

Position among storage technologies

Horizontal carousels compete with vertical carousels, vertical lift modules (VLMs) and shuttle-based goods-to-person systems. The horizontal type wins on throughput per dollar for medium-velocity small parts in buildings with normal ceilings: its mechanism is simple, one motor, one bearing surface, no lifts, and a pod scales by adding units rather than redesigning. It gives up storage density to VLMs, which exploit full building height, and absolute rate to shuttle systems, which cost an order of magnitude more. Its decades-old control architecture has aged well precisely because the mechanical core is a single loop with one degree of freedom.