The Diverter That Jammed the Boxes
We built a diverter (a pop-up arm) on a roller conveyor. It pushed boxes from the main line onto a side spur. On the bench, it worked. On the floor, the boxes jammed — the diverter arm hit the box’s bottom flap. The problem: the diverter was a flat plate that pushed the box by its side. But the box had a hanging bottom flap (the shipping box’s bottom). The arm caught the flap. We switched to a powered roller diverter (a set of rollers that rise and push the box from below). It lifted the box onto the spur. No jamming. The mistake was pushing the box by its side with a flat arm, instead of lifting it from below with powered rollers.
Conveyor diverter design routes products from one conveyor to another (or to a side spur). The method depends on the product. This article covers the choices.
Diverter Types
Pop-Up Wheel Diverter
A set of small wheels (or rollers) pop up above the conveyor surface. They push the product sideways (at 30° or 90°) onto a side conveyor. The wheels are powered (or the main conveyor pushes the product across them). Best for lightweight, rigid products (boxes, totes).
Best for: Boxes, totes, rigid products. Light-to-medium weight (under 20 kg).
Pop-Up Chain Diverter
A set of chains (perpendicular to the main conveyor) pop up. The chains carry the product off the line. Heavier than wheel diverters. For heavier products (totes, pallets).
Pusher Arm (Side Pusher)
A pneumatic arm pushes the product sideways off the conveyor. Simple, cheap. But it pushes by the side — can jam on irregular products (bags, soft packs). Best for rigid, uniform products.
Powered Roller Divert (90° Transfer)
A section of powered rollers (perpendicular to the main line) rises. The product is lifted off the main conveyor and carried 90° onto another line. For heavy or irregular products.
| Type | Product | Weight | Best For |
|---|---|---|---|
| Pop-up wheel | Rigid boxes/totes | Up to 20 kg | Light boxes, packaging |
| Pop-up chain | Totes, pallets | Up to 50 kg | Medium loads |
| Side pusher arm | Rigid, uniform | Up to 30 kg | Simple, cheap |
| Powered roller transfer | Any product | Any weight | Heavy, irregular, high speed |
Step 1: Product Type Determines the Diverter
The product dictates the diverter.
- Rigid boxes (corrugated): Pop-up wheel or side pusher. Fine.
- Soft bags or sacks: Don’t push from the side (they deform). Use a powered roller transfer or a belt diverter.
- Totes or pallets (heavy): Pop-up chain or powered roller.
- Irregular shapes (parts): Powered roller transfer (lifts from below, doesn’t care about the shape).
The diverter that jammed on boxes was a side pusher — it caught the bottom flap. A powered roller transfer (lifting from below) wouldn’t catch the flap.
Step 2: Timing and Sensing
The diverter must activate when the product is in position. A sensor (photoelectric) detects the product. When it’s centered over the diverter, the diverter raises (or the pusher fires).
- Input sensor: Detects the approaching product. The PLC knows a product is coming.
- Diverter sensor: Confirms the product is over the diverter (triggers the divert).
- After the divert: A sensor on the side conveyor confirms the product left the main line.
Don’t divert every product (only selected ones). The PLC decides: divert this one (go to the spur), or let it pass (continue on the main line).
The diverter rule: Match the diverter to the product. Rigid boxes = pop-up wheel. Heavy totes = pop-up chain. Irregular or soft products = powered roller transfer (lift from below). The diverter that jammed was a side pusher on a box with a hanging flap. Switch to a lift-from-below design.
Step 3: Diverter Speed
The diverter must act fast enough. If the conveyor runs at 30 m/min (0.5 m/s), the product moves 500 mm/s. The diverter must raise (or push) in under 0.2 seconds before the product passes.
Pneumatic diverters raise in about 0.3–0.5 seconds. For a fast conveyor (over 30 m/min), use a faster diverter (or slow the conveyor at the divert point).
Guide Rails on the Spur
The side conveyor (spur) has guide rails that keep the product aligned as it leaves the main line. The rails funnel the product onto the spur. Without them, the product might hang up at the junction.
Accumulation at the Divert
If the spur is full (products are waiting), the diverter shouldn’t push more products onto it. A sensor on the spur detects if it’s full. If full, the diverter doesn’t activate (products continue on the main line or wait).
A Diverter Checklist
- What is the product? (Box, tote, bag, part?)
- What is the product weight? (kg)
- What conveyor speed? (m/min)
- Diverter type? (Pop-up wheel, chain, pusher, roller?)
- Is the product rigid? (Side pusher OK, or lift from below?)
- Input sensor? (Detects approaching product.)
- Divert sensor? (Confirms product over diverter.)
- Does the diverter act fast enough? (Before product passes?)
- Guide rails on the spur?
- Is there a full-spur sensor? (Don’t divert if full?)
- Pneumatic or electric diverter? (Speed.)
- Does the diverter clear the line when not diverting? (No hang-ups?)
The Bottom Line
Conveyor diverter design matches the diverter type to the product. The diverter that jammed the boxes was a side pusher on a box with a hanging flap. For rigid boxes, use a pop-up wheel. For heavy totes, use pop-up chains. For irregular or soft products, use a powered roller transfer (lift from below). Sense the product position, time the divert, and add guide rails on the spur. The diverter that routes every product without jamming wasn’t the strongest arm — it was the right type for the product.
