1. Field of the Invention
This invention relates to apparatus for dividing heat-shrinkable plastic film into different temperature regions, for example one section of the heat-shrinkable plastic film has heat applied and another section of the film is isolated and maintained at a cooler temperature when passing through a heat shrink oven, for example. This allows a single shrink-wrap material to assume the characteristics of a shrunk portion and a non-shrunk portion.
The plastic film is shrunk over packages to secure the contents of the package and prevent damage to the contents of the package. Coils of wound filament material are often packaged in this manner. The invention has application to shrunk wrap packages in general and specifically to shrunk wrap packages of wound filament material wound in a figure-eight configuration known to the trade as a REELEX package.
An insulating barrier against the high temperatures typical of a heat shrink oven used to shrink wrap packages is achieved by a cylindrical tube mounted within the heat shrink oven and with a slit running along its entire length. At one end of the cylindrical tube a small section is cut away to provide a platform for resting a portion of the plastic shrink-wrap film prior to entry of the package into the shrink wrap oven and entry of the portion of the shrink wrap material into the slit in the cylindrical tube. The package and the portion of the film entering into the slit in the cylindrical tube travel the length of the oven together. An electric-operated cooling fan is mounted on the opposite end of the cylindrical tube. The fan forces cooler ambient air through the length of the cylindrical tube thereby maintaining a temperature inside the tube low enough to prevent shrinkage of that portion of the plastic shrink-wrap film as it passes through the cylindrical tube.
The cylindrical tube is then placed lengthwise inside the heat shrink oven, with the slit in the cylindrical tube facing towards the center of the oven. To operate the apparatus the electrical fan is switched on as the oven is turned on to suck ambient air into the end of the cylindrical tube with the platform and decreasing the temperature inside the cylindrical tube compared to the temperature inside the plastic shrink-wrap oven.
The portion of the plastic shrink-wrap film to be isolated from the heat of the oven is placed into the slit in the cylindrical tube and remains there the entire time the film and the package is inside the oven, thereby enabling the portion of the shrink-wrap film outside the tube to shrink and the portion of the shrink-wrap film inside the cylindrical tube to remain in its pre-shrunk form.
The above objects, features and advantages of the invention are readily apparent from the following description of a preferred embodiment of the best mode of carrying out the invention when taken in conjunction with the following drawings, wherein:
In
It is to be understood that while the invention ha general application to packages wound with shrink wrap material and to include a section that has no preshrunk material as described above, the invention has particular application to packages of coils wound in a figure eight configuration such as the REELEX packages known to the wound filament material trade.
In the isometric view of
From the above description it is readily apparent that the invention provides apparatus for dividing heat-shrinkable plastic film into different temperature regions, for example one section of the heat-shrinkable plastic film has heat applied and another section of the film is isolated and maintained at a cooler temperature when passing through a heat shrink oven, for example. This allows a single shrink-wrap material to assume the characteristics of a shrunk portion and a non-shrunk portion.