Bag blocks

Details Bag blocks Bag blocks

2002-02-15

2004-09-21

Sipos, John (Department: 3721)

Manufacturing container or tube from paper; or other manufacturi

Container making

Pliable container

C053S468000, C493S229000, C493S237000

Reexamination Certificate

active

06793613

ABSTRACT:

TECHNICAL FIELD OF THE INVENTION
The invention relates to thermoplastic bags that are stacked and blocked or unitized to be configured as a bag block. The bags can be stacked and/or dispensed using pre-punched holes (wicketed bag blocks), or stacked without use of such pre-punched holes (wicket-less bag blocks). Furthermore, the invention relates to a method of successively filling the bags and separating the filled bags from the bag block.
BACKGROUND OF THE INVENTION
Bag blocks are used in food packaging assembly lines for bagging successively delivered products such as bread loaves. The prior art related to the subject matter of the present invention includes U.S. Pat. Nos. 4,451,249; 4,342,564; and 4,699,607; PCT publication WO 99/48677; and European Patent EP 1 036 741, all herein incorporated by reference.
One conventional approach followed in producing a block of bags from folded or tubular webs of thermoplastic material is to seal and sever the web at equal intervals to produce a succession of bags which may be collected in a stack containing a desired number of bags. This approach may include concurrently processing more than one web strip to substantially increase the number of bags per unit time, a bag stack being generated from each web strip.
Particularly, the approach can involve sealing and severing tubular webs to produce a sheet having its marginal edges closed, defining a pillow. Each sheet is provided, at its medial zone, with spaced-apart lines of perforations and a succession of sheets are accumulated on a flat belt conveyor. Thereafter, the accumulated sheets are transported to a blocking and punching unit by the conveyor. At the blocking and punching unit a heated blade is passed through the sheets centrally between the lines or perforations, and substantially concurrently, a pair of wicket holes is formed on each side of the blade and between the lines of perforations, producing two wicketed bag blocks. The blocks can be carried by posts projected through the wicket holes. A bag can be dispensed from a block, being detached along the line of perforations, which defines the mouth of the bag.
In the manufacture of bag blocks, another approach is described in U.S. Pat. No. 4,699,607 which involves producing two bags from each web segment or sheet wherein each segment is provided with a line of perforations defining a generally circular enclosed area located equidistant from the opposed edges of the sheet. A stack of such sheets is carried by a support, supporting a central medial band of the sheets. The sheets are unitized or blocked by a heated member projecting through the sheets in the perforated circular area of the sheets. To produce individual bag blocks, the sheet stack is cut along a line through the central medial band of the sheets.
For a wicketed bag stack, holes can be pre-punched into the sheet within or outside of the circular perforated area, before the sheets are stacked, and posts are provided on the support for receiving the succession of sheets impaled thereon via the pre-punched holes. The subsequently blocked stack of wicketed bags is moved to a filling station wherein bags can be dispensed from the bag block by tearing individual bags from the bag block.
While U.S. Pat. No. 4,699,607 describes a manufacturing method wherein two bag blocks are formed simultaneously from a stack of double bag segments, which are subsequently separated into individual bag blocks, it is also known to form a single bag block in a similar fashion from a stack of single bag segments.
Another method of forming a bag block follows the following steps:
unwinding a layer of flat web of film from the unwind stand;
folding the web of film over a folding board;
applying a gusset in the web of film;
entering the web of film into the bag forming machine via the infeed section;
passing the intermittent moving part of the bag forming machine
whereby a number of operations are done to the web, including the application of a perforation pattern;
forming the bags by means of a sideweld or mixed weld sealing head;
picking up and stacking bags on an index conveyor or an automated wicket handling system; and
unitizing the stack of bags.
The unwind step can be accomplished by a standard Hudson-Sharp Machine Co. model SDU 1600 unwind stand. It is an electrical surface-driven and braked unwind with a compensator for perfect web tension control. A web guiding system ensures a centered web exiting the unwind stand.
The pre-centered web is pulled over the folding board by the infeed section of the bag machine, thereby forming a J-folded web whereby the lip is typically 35 to 45 mm wide. The folding board is a standard Hudson-Sharp Machine Co. 1500 mm folding board accessory. Optionally a bottom gusset is formed in the J-shaped web. The gusset former is a standard Hudson-Sharp Machine Co. 750 mm gusset former accessory.
The infeed section is the first section of the Hudson-Sharp Machine Co. model 4750W basic wicket machine. It pulls the J-folded web into the bag machine from the gusset former, folding board and unwind by means of a set of nip rolls typically driven by an AC motor. This AC motor is controlled by a frequency controller which obtains a speed reference from the main machine controller and the infeed dancer which is part of the infeed section and located just stream downwards of the nip rolls.
As a standard feature on the Hudson-Sharp Machine Co. model 4750W basic wicket machine, the intermittent moving part of the machine consists of two sets of servo driven nip rolls. In between the two pairs of nip rolls several attachments will modify the web of film such as by punching wicket holes for stacking and/or will detect the photo-eye mark for print registration. The formation of the bag is done in the sealing section of a standard Hudson-Sharp Machine Co. model 4750W. Typically the seals are side seals but mixed weld seals are also possible.
The picking up and stacking of the bags is done in the pick-up and conveyor section of a standard Hudson-Sharp Machine Co. model 4750W. Wicketed bags have wicket holes. Wicket holes have heretofore been circular, triangular, star shaped, or diamond shaped. The bags are stacked on wicket pins going through the wicket holes during stacking. Although this stacking method produces the most ordered stacking quality, it isn't a necessity. The bags can be made without any kind of stacking holes and be stacked on needles. The unitizing of the stack can be done with a standard Hudson-Sharp Machine Co. pin blocker. Accordingly, heated pins can be driven through the stack of bags. The unitizing is done in the lip area above a region of perforations. The subsequently blocked stack of wicketed bags is moved to a filling station wherein bags can be dispensed from the bag block by tearing individual bags from the bag block. During the filling operation perforations are broken to create an opening of each bag large enough to receive the product being packaged.
A method of filling and separating successive bags is described by the following steps:
putting a stack in a stack recipient box and indexing the box to the bag filling area;
opening the bag with an air nozzle or suction device;
inserting the bag opening device or spoons;
inserting the product into the bag;
pulling the bag off the stack together with the product; and
closing the bag and putting the bag on an offload conveyor.
The Ibonhart model IB 360 filler feeds each stack of bags into the filling area by means of a recipient box. In a preparation station, an operator puts a stack of bags into a recipient box. When the recipient box in the filling area is empty, it is transferred away from the filling area and a prefilled new recipient box is placed into the filling position. In this process the stacks are presented substantially horizontally in the recipient box. A slight downward angle in the gusset area (i.e., bottom area of the bags when oriented upright) can be applied to lower the gusset area.
Once the filling starts or restarts, bags are removed from the recipient box in the filli

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