This invention relates to an apparatus and process for the manufacture of flexible film articles such as zippered plastic bags, and more particularly, this invention relates to an apparatus and process for clamping, folding and transferring a stack of zippered plastic bags to a packaging operation.
The machinery used for the production of individual flexible web products such as plastic containers and bags is well known in the art. The machinery is sometimes referred to as a "bag sealer." For example, U.S. Pat. No. 5,014,978, incorporated herein by reference, discloses the type of equipment that is used for producing individual flexible bags. Ziploc.TM. is a brand of zipper type flexible bags. Generally, the machinery for making these bags includes a large diameter rotating drum which contains multiple heated wire severing and sealing elements positioned in grooves located within the outer periphery of the drum for severing and sealing a continuous web of thermoplastic material which has been folded upon itself to form two plies. The individual bags, are formed by severing portions of the thermoplastic material. The severed areas become side seams for the bags and are typically sealed at the same time as they are severed by the use of the heated wire elements. The individual bags are retained on the drum by a vacuum arrangement as the drum rotates.
The individual bags formed on the large rotating drum are taken from the drum by a smaller transfer drum, also suitably equipped with vacuum. The vacuum securing the bags onto the large drum is relieved at an appropriate point, and the bags fall onto the smaller drum where they are held in position by vacuum. At an appropriate point, the vacuum is released and the individual bags are pulled off the smaller drum by an orbital packer or similar device.
The orbital packing device is provided with a set of packer fingers which move in a circular path in precise timing with the smaller drum so that the fingers remove successive bags, which are typically separated on the drum approximately a nominal 1/8 inch from each other, from the drum and stack the bags on a stacking table against a backstop.
An apparatus including a set of clamping jaws, for example as described in U.S. Pat. Nos. 4,284,301 and 4,588,070, grasp the stack of bags at the stacking table and horizontally transfers the stack of bags from the stacking table to a horizontal support platform such as supporting bars or arms. Generally, at the horizontal support platform position, the stack of bags on the support platform is in a position normally directly above a dispenser loading station. Thus, a further means for transferring vertically the stack of bags from the support platform to a packaging point is then used. For example, an actuated elevator plate having a pair of bag clamps attached to it and capable of moving vertically up and down is used to transfer the stack of bags from the platform to a dispenser loading station. Sometimes the actuated elevator plate with bag clamps is referred to as a "first fold bag clamp and elevator apparatus."
The elevator plate with the bag clamps moves up to the support platform wherein the pair of bag clamps grip the stack at the stack's approximate centerline. Then, the cam actuated elevator plate, to which said bag clamps are mounted, lowers the stack vertically through a pair of guides which places a first fold into the stack as the elevator moves down to a position just below the guides. The guides restrain the stack in a first fold position until an awaiting open turret clamp closes on the stack. Then, the bag clamps are released and the turret begins to index 180 degrees from its dwell position. As the turret indexes, the once-folded stack of bags receives a second fold as the clamped stack passes a folding guide or shroud. The shroud holds the second fold until the turret stops rotating and the turret clamps are lowered into an awaiting dispenser (via a cam actuated carton load mechanism) at a position below the turret. The final orientation in the dispenser is in the form of a twice-folded stack of bags. The twice-folding apparatus and packaging procedure is described in co-pending U.S. patent application Ser. No. 07/786,861, filed Nov. 1, 1991, by Turvey et al., incorporated herein by reference.
The above bag sealer and twice-folding apparatus works well without having to use a side shift mechanism as described in U.S. Pat. Nos. 4,284,301 and 4,588,070, when used to produce and package "normal" sized commercially available bags, for example, quart size bags, sandwich size bags, gallon size bags and other bags of a greater size which are capable of being folded twice. However, producing and packaging a stack of bags of a size smaller than the smallest commercially available bag, for example a pint size bag which has the dimensions of 5 inches from zipper to fold, on existing bag sealer equipment is not practical without modification of the existing equipment. To run a different sized bag on an existing equipment originally made to run another certain sized bag requires a major modification to the existing equipment such as described in U.S. Pat. No. 4,588,070.
In a typical bag sealer for zippered bags, for example, the heat sealing and packaging functions in the equipment are based on a fixed location for the zipper profile. If the location of the incoming zipper profile is changed, such change, would be very expensive and require days, if not weeks, of machinery downtime.
In addition, since the stacks of bags are normally folded twice about the centerline of the stack and then inserted into a cardboard dispenser, producing bags of different depths (zipper to fold) requires the use of special machine features to reposition the centerline from that in the stacking position, to that for the first fold position. U.S. Pat. No. 4,588,070 illustrates one example of the need for repositioning a stack of bags in order for the existing bag-manufacturing and packaging equipment to be able handle a different size bag.
As aforementioned, any new proposed bags of a shallow depth, for example a depth of 3.25 inches (zipper to fold), would not be practical to fold the stack twice before insertion into a dispenser. As such, a single fold, or no fold, is desirable for this type of shallower product. Therefore, due to the product size and the impracticality of a double fold, the art practiced in U.S. Pat. No. 4,588,070 can not be utilized for repositioning the shallow depth bags contemplated herein.
One approach to producing and packaging shallow bags is to replace the seal drum, clamp assemblies, transfer drum, and packaging apparatus to change an existing machine over to machinery for handling a shallower bag. However, this approach would be cost prohibitive to any proposed new bag line extension. In fact, high capital to produce the product would probably cancel the project.
Accordingly, it is very desirable to utilize existing machinery and retrofit the machinery to handle smaller sized bags than heretofore produced with minimal modifications to the existing machinery.