Steam heated shrink tunnel

1 . An apparatus for shrinking film onto products moving along a conveyance path, comprising:

an elongated steam chamber shaped to form a shrink tunnel through which the conveyance path extends, wherein the elongated steam chamber includes spaced apart interior walls and exterior walls that define an interior steam flow space therebetween, wherein the interior walls define tunnel bounding wall portions that at least partly delimit the shrink tunnel at least in tunnel regions above a plane of the conveyance path, the tunnel bounding wall portions including inner surfaces facing and exposed to the shrink tunnel and outer surfaces facing and exposed to the interior steam flow space, wherein a steam input is provided for flowing steam into the interior steam flow space such that the steam fills the interior steam flow space, and the tunnel bounding wall portions are heated by steam flowing through the interior steam flow space over and in contact with the outer surfaces of the tunnel bounding wall portions, and the tunnel bounding wall portions thereby radiate heat into the shrink tunnel, an outlet from the interior steam flow space being formed in at least one of the exterior walls;

at least one steam header positioned within the shrink tunnel between the tunnel bounding wall portions and the conveyance path and extending along at least part of a length of the shrink tunnel, the at least one steam header including steam ejection orifices for ejecting steam into the shrink tunnel, the at least one steam header including a steam input located outside the shrink tunnel; and

at least one steam flow tube running from the outlet, and outside of the shrink tunnel, for feeding steam from the outlet of the interior steam flow space to an input of the at least one steam header;

wherein the tunnel bounding wall portions include wall portions above the shrink tunnel and along side regions of the shrink tunnel.

2 . The apparatus of claim 1 , wherein the tunnel bounding wall portions of the elongated steam chamber are maintained at 212° F. or above during shrink operations.

3 . The apparatus of claim 1 , wherein a pressure within the interior steam flow space is maintained at 1 psi or above during shrink operations.

4 . The apparatus of claim 1 , wherein the interior steam flow space functions as a steam manifold through which steam progresses to reach the outlet.

5 . The apparatus of claim 4 , further comprising:

a steam boiler for heating water to produce steam, the steam boiler including an output that is connected to feed steam to the steam input.

6 . The apparatus of claim 5 , wherein the interior steam flow space includes multiple outlets, the at least one steam flow path comprises multiple steam flow paths, and the at least one steam header comprises multiple steam headers running along side portions of the shrink tunnel.

7 . The apparatus of claim 1 , wherein the at least one steam header is formed by at least one steam pipe positioned at least partly within the shrink tunnel, wherein the at least one steam pipe is mounted to permit tool-free rotation for adjusting a directional output of the steam injection orifices.

8 . The apparatus of claim 7 , wherein the at least one steam flow path comprises a flexible tubing that is connected to an input end of the at least one steam pipe, wherein the input end of the at least one steam pipe is positioned externally of the shrink tunnel and carries an adjustment handle to enable manual rotation of the at least one steam pipe.

9 . The apparatus of claim 8 , wherein a clamp frictionally engages the input end of the at least one steam pipe for inhibiting incidental rotation of the at least one steam pipe, and a torque force applied via the handle must exceed a frictional holding force of the clamp in order for the at least one steam pipe to be rotated.

10 . The apparatus of claim 1 , wherein the elongated steam chamber includes at least one heating element positioned within the interior steam flow space for heating steam within the interior steam flow space such that the elongated steam chamber functions as a superheater during shrink operations.

11 . The apparatus of claim 1 , wherein the interior walls form a first inverted U-shape to define the shrink tunnel, wherein the exterior walls form a second inverted U-shape that is spaced from and overlaps the first inverted U-shape to at least in part define the interior steam flow space of the elongated steam chamber.

12 . An apparatus for shrinking film onto products moving along a conveyance path, comprising:

an elongated steam chamber including an interior steam flow space along which steam travels, wherein the elongated steam chamber is shaped to form a shrink tunnel through which the conveyance path extends, wherein the elongated steam chamber includes tunnel facing walls that separate the interior steam flow space from the shrink tunnel, wherein the tunnel facing walls include inner surfaces facing and exposed to the shrink tunnel and outer surfaces facing and exposed to the interior steam flow space, wherein a steam input is provided for flowing steam into the interior steam flow space, wherein steam traveling within the interior steam flow space and in contact with the outer surfaces of the tunnel facing walls heats the tunnel facing walls, and the tunnel facing walls thereby radiate heat into the shrink tunnel, the interior steam flow space including output openings;

steam pipes positioned at least partly within the shrink tunnel, each steam pipe extending along at least part of a length of the shrink tunnel, each steam pipe separated from the interior steam flow space by the tunnel facing walls, each steam pipe including steam ejection orifices for ejecting steam into the shrink tunnel; and

a plurality of steam flow tubes, each steam flow tube connected to feed steam from one of the output openings of the interior steam flow space to one of the steam pipes, each steam flow tube running outside of the shrink tunnel;

wherein the interior steam flow space functions as a steam manifold through which steam progresses to reach the output openings.

13 . The apparatus of claim 12 , wherein the tunnel facing walls are maintained at 212° F. or above during shrink operations, and a pressure within the interior steam flow space is maintained at 1 psi or above during shrink operations.

14 . The apparatus of claim 12 , wherein the elongated steam chamber includes exterior walls spaced apart from the tunnel facing walls such that the interior steam flow space is defined between the exterior walls and the tunnel facing walls, wherein the output openings are located on at least one of the exterior walls, wherein each steam pipe includes an end portion outside of the shrink tunnel.

15 . An apparatus for shrinking film onto products moving along a conveyance path, comprising:

an elongated steam chamber including an interior steam flow space along which steam travels, wherein the elongated steam chamber is shaped to form a shrink tunnel through which the conveyance path extends, wherein the elongated steam chamber includes at least one tunnel bounding wall that separates the interior steam flow space from the shrink tunnel, wherein the at least one tunnel bounding wall includes an inner surface facing and exposed to the shrink tunnel and an outer surface facing and exposed to the interior steam flow space, wherein a steam input is provided for flowing steam into the interior steam flow space, wherein steam traveling within the interior steam flow space and in contact with the outer surface of the at least one tunnel bounding wall heats the at least one tunnel bounding wall, and the at least one tunnel bounding wall thereby radiates heat into the shrink tunnel, the interior steam flow space including at least one outlet opening;

at least one steam header positioned at least partly within the shrink tunnel and extending along at least part of a length of the shrink tunnel, the steam header including steam ejection orifices for ejecting steam into the shrink tunnel; and

at least one steam flow tube connected to feed steam from the at least one outlet opening of the interior steam flow space to the at least one steam header.

16 . The apparatus of claim 15 , wherein the at least one steam header comprises a first steam pipe.

17 . The apparatus of claim 16 wherein the first steam pipe is mounted to permit tool-free rotation of the first steam pipe, for adjusting a directional output of the steam injection orifices.