Shrink tunnel

A shrink tunnel or heat tunnel is a heated tunnel mounted over or around a conveyor system. Items (such as packaging) have shrink film loosely applied; with heat, the film shrinks to fit snugly around the wrapped object.^[1]

Heat tunnel for shrink wrapping bakery goods

in-line heating of shrink bands on plastic bottles of water

Machinery to apply and shrink an overwrap

Uses

• Shrink labels.
• Combining small items for sale and display (example: bottled water).
• Tamper resistant or Tamper-evident bands or seals.^[2]
• Form large unit loads for transport.
• Form primary barrier on foods such as cheese, meats and fish.
• Skin packs.

Types

Several types of shrink tunnels are available.^[3][4][5] The heat source can be based on heating element (electrical resistance), infrared heater, steam, or gas flame. Often forced air is used to improve convection, sometimes focusing the heat on one component of the item.

Tunnels are available with or without a conveyor system. Some are built into a production line or are integral with machinery that also applies the shrink film. Others are movable by hand or by castors. A shrink tunnel, referred to as an oven, may be equipped with an integrated conveyor of two different kinds: the roller conveyor or the belt conveyor. Roller conveyors can be used with polyolefin, PVC, and shrink polyethylene films. The space in between the rollers is filled with hot air from the bottom of the tunnel to shrink the film layer around the object, creating a sealed package. When used with polyolefin and PVC based films the rollers are called "live" or spinning. When used with polyethylene films the rollers are called "dead" or not spinning. The tunnels with Teflon mesh belts and polymer mesh belts are used for smaller packages, or when the package may have an instability and need a stable platform.

Some heat shrink tunnels have two or more zones for heating and controlled cooling.

See also

• Heat gun

References

1. Soroka, W (2008). Illustrated Glossary of Packaging Terms. Institute of Packaging Professionals. p. 33. ISBN 978-1-930268-27-2.
2. US 5390477, Sowden, Harry, "System for applying a heat shrinkable sleeve to a container", published 1995-02-21, assigned to McNeilab Inc.
3. US 3591767, Mudie, David Jeffrey, "Radiant shrink tunnel", published 1971-07-06
4. US 5740659, Cox, John Farrell; Fiesser, Frederick Henry & Jeral, Robert Vincent et al., "Shrink tunnel and methods relating thereto", published 1998-04-21, assigned to E.I. du Pont de Nemours & Co.
5. US 7155876, VanderTuin, Bradley Jon; Schoeneck, Richard Jerome & Pazdernik, Irvan Leo et al., "Heat tunnel for film shrinking", published 2007-01-02, assigned to Douglas Machine Inc.

• Soroka, W, "Fundamentals of Packaging Technology", IoPP, 2002, ISBN 1-930268-25-4
• Yam, K. L., "Encyclopedia of Packaging Technology", John Wiley & Sons, 2009, ISBN 978-0-470-08704-6