Importance

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Abstract

A bag-making machine is disclosed for producing bags from thermoplastic web material. A device (86) for grasping and transferring web segments in an arcuate path for reception by an accumulating device (88) serves to grasp adjacent opposed edges and transfers them through an arc to an accumulating device which includes posts (90). Accumulation of web segments occurs on a bag stack accumulating and transporting device located between laterally spaced radially projected arms of the web transfer device and it includes an indexing system (94) for translating the stacking posts away from the stacking station. The web segments are subsequently cut and/or joined along a line located centrally of the web segments at a station (102) to thereby produce two individual stacks of bags. This invention relates to a method of and apparatus for producing thermoplastic bags. Machines for producing bags from thermoplastic web material come in a variety of configurations depending upon the size and style of bags to be produced and are adaptable to process material of various thicknesses and chemical compositions. Certain bag machines are dedicated to produce one style of bag (side weld or bottom weld) or their design is of a universal character such that by replacement of certain components side weld or bottom weld bags can be made. Directly or indirectly the object of bag machine developments is to decrease the time to produce a bag. The most important consideration in reducing machine cycle time is substantially wholly dependant upon whether the output of the bag machine can be organized such that successive bags are accumulated in neatly registered stacks with each stack containing a predetermined number of bags. One approach currently practiced to produce registered counted stacks is to utilize a bag stack accumulating conveyor, known as a wicketer. Basically, the accumulating conveyor includes a plurality of sets of pins which are successively positioned at a stacking station and remain there until a predetermined number of bags have been deposited on the pins. By using this procedure each individual bag is provided with a pair of holes whose pitch matches the spacing of the wicket pins. After a predetermined number of bags have been accumulated, advance of the web is arrested and the conveyor carrying the set of pins is indexed to transport a completed bag stack away from the stacking station and to position a succeeding pair of pins at the stacking station. Machines utilizing a wicket stacker are in very wide use because stacks of several hundred bags of low gauge high density polyethylene can be quickly and accurately stacked since windage problems have a very minimal effect on proper stacking. According to the present invention in one aspect, there is provided a method of producing thermoplastic bags characterized by the steps of producing segments each defining two bags, transferring the segments successively on one stacking device of an indexing conveyor having a plurality of said stacking devices spaced along its length and engaging the segments on the stacking device at at least one point whereby to retain the segments as a registered stack, and severing the segments of the stack after indexing from the location at which the segments are received on any given stacking device. According to the present invention in a second aspect, there is provided apparatus for producing thermoplastic bags characterized by means for producing segments each defining two bags, means for transferring the segments successively on to one stacking device of an indexing conveyor having a plurality of said stacking devices spaced along its length and means for engaging the segments when on any given one of said stacking devices at at least one point whereby to retain the segments as a registered stack, and means for severing the segments of the stack after indexing from the location at which the segments are received on any given stacking device. When it is desired to produce bags from tubular film, certain considerable advantages result in printing the web on one or both sides. More particularly the pattern achievable by the printing press can be duplicated on either side of the longitudinal median of the web, because processing by the bag machinery constructed in accordance with the principles of this invention allows creation of two bags from a web segment. The rate at which bags made from thermoplastic web material can be produced by both aspects of the invention is double the rate of machine cycle time and the physical characteristics of the material, such as its lack of stiffness, is no longer a factor limiting accurate stacking and stack maintenance when accumulated stacks are transferred to further processing apparatus. More particularly, the process and apparatus of the present invention allow rapid controlled transfer and the creation of stacks containing several hundred web segments when processing the thinnest available low density polyethylene.

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First Claim