Package making – Methods – Forming a cover adjunct or application of a cover adjunct to...
Reexamination Certificate
1998-12-03
2001-02-13
Johnson, Linda (Department: 3721)
Package making
Methods
Forming a cover adjunct or application of a cover adjunct to...
C053S451000
Reexamination Certificate
active
06185908
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to packaging materials used in automatic form, fill and seal machines. In particular, the invention relates to the use of thermal plastic mesh web as a packaging material for automatic form, fill and seal machines.
BACKGROUND OF THE INVENTION
Mesh bags are used to package various products, for instance, produce is often packaged in mesh bags to allow the produce to breath. Thermal sealable plastic mesh is often used to allow efficient application of thermal sealable print bands to the mesh for labelling and advertising. The mesh bags are preformed and filled either manually or semi-automatically. Thermal sealable plastic mesh is often used to allow efficient application of thermal sealable print bands to the mesh for labelling and advertising. The bottom cross seam of the preformed bags is normally sewn across the entire transverse length of the bag to provide sufficient bag strength. In the semi-automatic process, the preformed bag is secured to a filling mandril, the produce is manually put into the bag, and the top of the bag is hog-tied or crimped shut with a ring. This type of loading is labor-intensive and costly.
Automatic form, fill and seal machines are widely used in the packaging industry and significantly reduce packaging costs, especially labor costs associated with loading. Conventional automatic form, fill and seal machines contemporaneously form, fill and seal a bag from a heat sealable film continuously unwound from a roll. The process involves forming a tube from a layer of the heat sealable film unwound from the roll and heat sealing the longitudinal edges of the film together to form a back seam for the bag. The back seam is typically either a lap seal or a fin seal. The sealed tube is then pulled or driven downward for a distance equalling the length of the bag being formed. Transverse heat sealing jaws close to contemporaneously form the bottom cross seal for the bag and the top cross seal for the previous bag. The cross seal is cut and the previous bag falls into a bin or onto a conveyor, etc. At the same time, the open bag is filled. Automatic form, fill and seal machines are either gravity fed (e.g. vertical form, fill and seal machines) or mechanically fed (e.g. horizontal form, fill and seal machines).
Automatic form, fill and seal machines are efficient and cost effective when using many types of non-mesh films. However, bags produced from form, fill and seal machines using thermal sealable mesh have insufficient seam strength along the bottom and top fin seal for most practical uses. Therefore, to date, virtually all mesh bags are pre-formed with a sewn bottom cross seam.
SUMMARY OF THE INVENTION
The invention involves the use of a pre-prepared web of thermal sealable plastic mesh that includes equally spaced pre-attached filler strips of thermal sealable material. The filler strips are preferably cut from a film of solid thermal sealable material, such as polyethylene film having a thickness between 1 to 6 or possibly more mils. Such pre-prepared web enables practical use of thermal sealable mesh on conventional or slightly modified form, fill and seal machines. The filler strips are preferably located transverse along the mesh web and spaced apart equally at a distance equal to the length of a mesh bag. The filler strips provide an adequate mass of thermal sealable material along the top and bottom fin seals of the mesh to provide sufficient seam strength in practical applications.
The filler material preferably lies between the layers of bonded mesh at the transverse fin seal when the bag is formed and sealed. In order to provide an adequate seal, it is normally necessary to apply only one layer of filler material, for example 1-6 or more mils of polyethylene film or other heat sealable film, between the bonded layers of thermal sealable plastic mesh. In order to ensure adequate strength at the edges of the transverse fin seals, it may be desirable for the filler strip to double back slightly at the edges.
In most applications, it is desirable to also pre-attach a longitudinal print band to the side of the mesh web opposite the filler strips. In applications using longitudinal print bands, it may not be necessary to provide the filler strip for the portion of the cross seal where the print band is present, however, even in these applications it will be preferred to provide the filler strip across the entire transverse length of the cross seal.
In one preferred embodiment of the invention, the pre-prepared mesh web includes a longitudinal print band that is heat sealed and centered on one side of the thermal sealable plastic mesh web as is known in the art. On the other side of the mesh web, transverse filler strips of thermal sealable material for the top and bottom cross seals are centered over the print band. When the mesh web is run on a conventional form, fill and seal machine, the outer portions of the mesh web are preferably formed into a lap configuration for a back seal. The back seal is formed using a conventional heat sealing bar and the fin seals for the top and bottom cross seals are formed using a conventional heat sealer and cutter.
In some applications, it may be desirable to provide a fin seal for the back seal instead of an lap seal. In these applications, the pre-prepared mesh web should also include a continuous longitudinal strip of thermal sealable filler material along one of the longitudinal edges of the mesh web. In this manner, a reliable fin seal for the back seam can be formed on a conventional form, fill and seal machine modified to form a fin seal at the back seam. Such a continuous longitudinal strip can also be used to strengthen a lap seal.
Some automatic form, fill and seal machines have the ability to apply thermal sealable tape along the longitudinal seam during the forming process. Conventional thermal sealable tape often includes a zipper, although thermal sealable tape without a zipper is available. Thermal sealable tapes are folded when purchased in rolls from suppliers. The tape is typically applied during the form, fill and seal process by folding the web along a longitudinal seam and thereafter thermally attaching each side of the tape to the respective free edge of the folded web. For a form, fill and seal machine that applies a zipper, the thermal sealable filler strips on the mesh web are specifically configured. When using a pre-prepared thermal sealable plastic mesh web in this application, it is important that the thermal sealable filler strip be located properly on the mesh web so that thermal sealable filler material spans along the entire top and bottom cross seams when the bag is formed. Normally, this means that filler strips extend laterally from the longitudinal centerline of the mesh web outward in one transverse direction to a longitudinal edge of the mesh web.
Other features and advantages of the invention may be apparent to those skilled in the art upon inspecting the following drawings and description thereof.
REFERENCES:
patent: 2512216 (1950-06-01), Salfisberg
patent: 2687764 (1954-08-01), Hauser
patent: 2815620 (1957-12-01), Prodigo
patent: 2992146 (1961-07-01), Drelich
patent: 3173232 (1965-03-01), Mercer
patent: 3293824 (1966-12-01), Dorr
patent: 3432980 (1969-03-01), Seiferth et al.
patent: 3732666 (1973-05-01), Nakamura
patent: 3939628 (1976-02-01), Schjeldahl
patent: 3996721 (1976-12-01), Mercer
patent: 4282055 (1981-08-01), Bosse et al.
patent: 4288965 (1981-09-01), James
patent: 4291082 (1981-09-01), Stall
patent: 4322929 (1982-04-01), Neumann
patent: 4355494 (1982-10-01), Tilman
patent: 4532754 (1985-08-01), Hokanson
patent: 4554202 (1985-11-01), Kamei et al.
patent: 4563231 (1986-01-01), Porrmann et al.
patent: 4617683 (1986-10-01), Christoff
patent: 5117612 (1992-06-01), Keim et al.
patent: 5369936 (1994-12-01), Callahan et al.
patent: 5529659 (1996-06-01), Ellsworth et al.
patent: 5552165 (1996-09-01), Haak et al.
patent: 5729961 (1998-03-01), Dauder-Guardiola
Fox fresh mesh—Admitted Prior Art.
High Speed Three Side Seal Pouc
Andrus Sceales, Starke & Sawall
C&H Packaging Company, Inc.
Johnson Linda
LandOfFree
Thermal sealable plastic mesh web for automatic form, fill... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Thermal sealable plastic mesh web for automatic form, fill..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Thermal sealable plastic mesh web for automatic form, fill... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2578825