Package making – Methods – Forming or partial forming a receptacle and subsequent filling
Reexamination Certificate
1999-02-12
2001-08-28
Kim, Eugene (Department: 3721)
Package making
Methods
Forming or partial forming a receptacle and subsequent filling
C053S559000, C053S567000
Reexamination Certificate
active
06279300
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention relates generally to packaging and, more particularly, to new methods of forming an air cell bubble sheet or dunnage for cushioning objects to be transported to prevent impact or shock damage.
2. Description of the Prior Art
It is known in the art to protect items to be shipped from damage with layered sheet-like bubble wrap. A typical prior art air cell dunnage is formed as a multiple layer assembly, which includes a thin, flat base layer and an overlying bubble layer. The bubble layer is formed from a flat plastic sheet having a thickness greater than the base layer. In the instance of relatively large bubbles, e.g., one inch diameter, the thickness ratio of the bubble sheet relative to the base layer is about 2:1. For smaller bubble diameters, e.g., {fraction (5/16)}″, this ratio decreases to about 3:2. The bubble layer is fabricated by vacuum forming the flat plastic sheet using hemispherical female dies. This bubble layer is fused to the base layer, to form a laminate having a number of airtight cells for supporting or cushioning packaged items.
One problem associated with conventional sheets is the uneven bubble wall thickness after vacuum forming. This condition is exacerbated with large bubble diameters. The larger the bubble diameter, the greater the distance between the apex of the bubble and the base. The vacuum forming process causes the plastic to stretch from the base toward the apex of each bubble, and results in a relatively thinner wall thickness in the apical region. Consequently, after the sheet is drawn down, the final bubble sheet thickness may be too thin near the bubble apex to provide the required structural integrity. To ensure that an adequate wall thickness remains in the apical region of the bubbles after forming, the initial wall thickness of the bubble sheet must be greater than twice the thickness of the base layer.
To protect an object for shipping, a carrier or consumer snugly wraps a conventional bubble sheet around the object with the bubbles pressed between the object and the interior surfaces of a box. The bubbles provide an air cushion around the object, which suspends and protects it from shock induced damage if the box is dropped or subjected to impact.
To ensure an adequate bubble wall thickness in the final product, it is necessary to use more material than required. This is an inefficient way to manufacture the air cell dunnage and a waste of material resources.
Although conventional dual layered bubble sheet designs work as intended, a single bubble wrap as a buffer may not adequately protect the object if some of the bubbles adjacent to the packed object are caused to prematurely burst. To provide adequate anti-shock protection, commercial carriers therefore may wrap the object several times with conventional bubble sheets. This arrangement provides at least one backup bubble layer to protect the object if some of the bubbles become damaged. However, wrapping the object in multiple layers of bubble material, or having to stuff unoccupied areas of the container with “filler” material is a waste of plastic. Ultimately, higher costs are passed on to consumers, and a negative environmental impact results as more plastic material is discarded.
It is an object of the invention to provide improved air cell dunnage for protecting packed items during shipping.
It is another object of the present invention to provide air cell dunnage which can be manufactured with reduced raw material costs.
It is a further object of the present invention to provide air cell dunnage which reduces detrimental effects of material waste on the environment.
It is yet another object of the present invention to provide air cell dunnage for protecting packed items during shipping, with reduced material requirements.
It is still another object of the present invention to provide air cell dunnage which maximizes structural integrity through a molding process which minimizes material thickness disparities.
SUMMARY OF THE INVENTION
The invention provides a number of different ways of manufacturing air cell dunnage in which the variation in the thickness of the bubble wall is significantly reduced. In one embodiment, the bubbles are formed from a plastic sheet having regions which vary in thickness so that when these regions are vacuum formed into bubbles, they result in bubbles having an approximately uniform wall thickness. The sheets may be formed by extrusion through a die which is shaped to profile the thickness of the sheet from side to side. Further profiling of the thickness can be provided by means of shaping bars which move vertically with respect to the extruded sheet to vary the thickness profile longitudinally.
It is also contemplated that the variation in wall thickness can be reduced using a conventional plastic sheet by controlling the application of the vacuum to the hemispherical dies which form the bubbles. In one embodiment, the vacuum is applied progressively through rings of apertures from the bottom or opening of the bubble to the top or apex of the bubble. This increases stretching of the plastic at the base and reduces it at the top, resulting in a more uniform wall thickness. Alternatively, the suction applied to the various rings of apertures in the hemispherical dies can be varied, with greater suction applied at the base and less suction at the top, again for the purpose of increasing stretching at the base and reducing it at the top.
In accordance with another aspect of the invention, a substantial savings in the material requirements of air cell dunnage is achieved by providing a double-sided bubble sheet. To accomplish this, two bubble layers are formed in any manner including the way described above. The two bubble layers are then joined to opposite sides of a base layer. Alternatively, each of the bubble layers may be joined to a thin base layer and the base layers laminated together to form a double-sided bubble sheet.
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Darby & Darby
Kim Eugene
LandOfFree
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