Sliding-Shoe Sorter

Overview

A sliding-shoe sorter is a conveyor that sorts by pushing items sideways off a moving bed with diverting shoes rather than by tipping them or running them onto a cross belt. The bed is a deck of slats, and beside each row of slats sit low plastic shoes that normally rest out of the way at the side. To divert an item, a group of shoes slides diagonally across the slats and gently sweeps the item off the bed into a take-away lane. Because the push is a soft, angled sweep across the full length of the item, the machine handles heavy cartons and totes without jarring them, which is why it is the standard carton sorter in distribution centres and parcel operations.

The sorter is built from a Slat Conveyor Bed that carries items, the Diverting Shoes that do the pushing, a Shoe Switch System that steers the shoes, a Drive and Take-Up that pulls the bed, the Divert Lanes and Chutes that receive items, a Conveyor Frame that holds it all flat, and a Sortation Control that decides where each item goes.

The slat bed

The conveying surface is the Slat Conveyor Bed, a deck of extruded Conveyor Slat slats running on two Slat Chain chains, one down each side. Each slat carries a groove on top that a shoe rides in, and the slats run on Chain Roller rollers in the frame so the bed stays flat. The slat chains are built from hardened Chain Link links and Chain Pin pins, and in the divert zone the slats slide on Wear Strip wear strips. The whole bed moves as one surface, carrying items along while the shoes sit ready at the side.

How a shoe diverts

The sort is done by the Diverting Shoes. Each Diverting Shoe is a low block that rides in a slat groove, normally parked at one edge of the bed. Under the bed every shoe carries a Guide Pin guide pin, and the path of that pin decides where the shoe goes. Most of the time the pin follows a straight rail and the shoe stays at the side. To divert an item, the Shoe Switch System raises a Divert Rail into the pin path for one lane, which steers a run of shoes diagonally across the bed. As those shoes cross, their soft Contact Pad faces meet the item and sweep it off the bed and down the lane. The diagonal sweep is gentle and progressive, so the item turns and slides off rather than being struck, and after the divert a Home Rail returns all the shoes to the side ready for the next item.

Switching and timing

The Shoe Switch System is what makes the divert happen at the right moment. Each lane has a Divert Rail thrown by a Switch Actuator and a Air Cylinder, fed air through a Solenoid Valve. The control fires the right lane just as the leading slat of the item reaches it, and the rail stays raised long enough for exactly the run of shoes that spans the item, then drops so following items pass undisturbed. Because diverts can be set on either side of the bed, the machine sorts left and right, and several diverts can be active at once for different items spaced down the bed.

Drive and frame

The Drive and Take-Up pulls both slat chains together. A Drive Gearmotor turns a Drive Shaft carrying two Drive Sprocket sprockets so the chains stay in phase, and a tail Chain Take-Up keeps them evenly tensioned as they wear. The bed sits in a Conveyor Frame built on a welded Frame Weldment that holds it flat and straight, with Side Guide rails to keep items on the bed until their divert and Leveling Foot feet to level the long machine.

Lanes and take-away

A diverted item leaves the bed into the Divert Lanes and Chutes. Each lane starts with an angled Lane Chute that guides the swept item off the bed, and most lanes feed a powered Take-Away Conveyor that carries items to a packing or staging area. A Lane-Full Sensor on each lane signals when it is backed up so the control pauses sorting there. The number of lanes sets how many destinations the sorter serves, and lanes can be placed close together because each divert needs only a short stretch of bed.

Control and use

The Sortation Control runs the sort. A Barcode Scanner reads each item upstream, a Sort Controller maps the label to a lane, and a Bed Encoder tracks bed travel so the controller knows exactly which slats the item sits on. The controller fires the lane diverts through its outputs as the item arrives, holds bed speed steady through a Variable-Frequency Drive, and uses Photoeye sensors to confirm presence and track gaps. Sliding-shoe sorters are chosen where the load is mostly cartons and totes and gentle handling matters, and they scale from short units with a handful of lanes in a retail back room to long high-rate beds with dozens of lanes in a large distribution centre. Their advantage is the positive, full-length sweep, which moves heavy and large items reliably without the impact of a pusher or the balance limits of a tilting tray.