Backaround of the Invention The patented pnor art relating to the suoject matter of the present Invention includes U. S. Patent No 4. 451.249 : 4. 342.564 : and 4.699.607. all herein incorporated by reference. Bag blocks are used in food packaging assembly lines for bagging successively delivered products such as bread loaves.

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 mclude concurrently processing more than one web stnp to substantially increase the number of bags per unit time. a bag stack being generated from each web stnp.

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.

Another approach, such as described in U. S. Patent 4. 699.607. 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 unified or blocked by a heated member projecting through the sheets in the perforated circular area of the sheets. If it is desired to produce individual bag blocks. the sheet stack is cut along a line through the central medial band of the sheets.

The support can include sharpened pins or needles to puncture and penetrate the sheets as they are deposited on the support. and serve to firmly retain successive sheets so that a registered stack (meaning that the marginal edges of successive sheets overly each other) is produced.

For a wicketed bag stack, holes can be prepunched into the sheets within 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 prepunched holes. The subsequently blocked stack of wicketed bags can be dispensed at a filling

location by tearing individual bags from posts supporting the stack via the prepunched holes.

While U. S. Patent 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.

The present inventor has recognized the desirability of minimizing wasted web material which results from forming bags from webs and thereafter teanng off bags from a block of bags. The present inventor has recognized the desirability of providing a block of bags which dispenses individual bacs with a minimized but precise tear off force.

Summary of the Invention The present invention contemplates an improved design for wicketed and wicket- less blocked bag stacks or"bag blocks wherein a top bag of the block is removed from the stack with a minimum waste of web material and with a minimized but precise tear off force.

In a first aspect of the invention. at each side edge of a bag. a line of perforations extends inwardly perpendicularly to the side edge. for a short distance. A straight line cut. or two straight line cuts separated by a connecting web. extends from an end of the line of perforations obliquely toward a top edge of the bag. A plurality of such bags are collected in a stack. A hot blade is driven through corner tear off regions defined by the adjacent side and top edges of each bag. the straight line cut. and the

line of perforations, to unitize or block the stack of bags. This embodiment can be incorporated into a wicket-less or wicketed bag. Additionally, at the top edge of the bag where the straight line cut or two cuts approach the top edge. a nick can be provided into the top edge for ensuring precise tear off of the corner regions of the bag.

In another aspect of the invention two substantially rectangular tear off regions are provided at the upper corners of a bag. The tear off regions are each defined by adjacent side and top edges of the bag, a short line of perforations extending inwardly from the side edge of the bag, and a shaped cut. or plural cuts separated by one or more connecting webs, and extending from an end of the short line of perforations.

The shaped cut or plural cuts extend upwardly to approach a top edge of the bag. A nick can be provided into the top edge of the bag approaching, or in registry with. the shaped cut or plural cuts to ensure precise separation of the corner tear off regions.

Wicket holes can be provided within the corner tear off regions. A hot blade is passed through the stack of bags, within each of the tear off regions, to unitize the stack of bags as a bag block.

In either of the embodiments, rather than the hot blade penetrating through the tear off region, the stack of bags can be unitized by a hot blade being applied to a top edge of the stack of bags. Either a flat blade or a cylindrical pin can be used to unitize a top region of the stack. Alternatively. the wicket hole itself can be the location of unitizing around its inner circumference. Furthermore. rather than a single flat hot blade unitizing a flat region of the stack of bags, a plurality of hot pins. arranged in parallel. can be applied to a top surface of the stack of bags in order to unitize the bag stack.

It may be important in some applications. particularly in an assembly line bag filling operation, that each successive bag is removed with a minimum and precise flexibility to achieve this tear off force.

The lateral line of perforations are torn with a minimum of force. The tear off force is perpendicular to the line of perforations so that tensile stress on the residual web material is maximum and shear stress is minimum. The region of shear stress. a vertical region, is made minimum by the use of cuts rather than perforations.

The dimension between the corner tear off regions is maximized and the vertical dimension of the tear off regions is minimized. In this way web material is conserved during manufactunng and usage of the bags.

Numerous other advantages and features of the present invention will become readily apparent from the following detailed description of the invention and the embodiments thereof, from the claims and from the accompanying drawings.

Brief Description of the Drawings FIGURE 1 is a perspective view of a first embodiment stack of bags in accordance with the present invention : FIGURE 2 is a perspective view of a second embodiment stack of bags in accordance with the present invention : FIGURE 3 is a perspective view of a third embodiment stack of bags in accordance with the present invention : FIGURE 4 is a perspective view of a fourth embodiment in accordance with the present invention :

FIGURE 5 is a perspective view of a fifth embodiment in accordance with the present invention : FIGURE 6 is a schematic diagram illustrating a method of forming bag blocks according to the invention ; and FIGURE 7 is an enlarged fragmentary plan view taken from FIGURE 6.

Detailed Description of the Preferred Embodiments While this invention is susceptible of embodiment in many different forms, there are shown in the drawings, and will be described herein in detail, specific embodiments thereof with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the invention to the specific embodiments illustrated.

Exemplary apparatus for manufacturing, stacking and blocking bag stacks are described in the aforementioned U. S. Patent 4, 699, 607.

FIGURE 1 illustrates a stack 20 of bags 24 according to a first embodiment of the invention. Each bag 24 includes a tubular body 26 having a front wall 28 and a back wall 32 which extends upwardly of the front wall. forming a back top panel or flap 36. The bag body has first and second sealed side edges 40. 42. a top edge 46. and a bag mouth 47.

Extending perpendicularly and inwardly from the first side edge 40, is a first line of perforations 52. Extending perpendicularly and inwardly from the second side edge 42. is a second line of perforations 54. A first angular cut 56 extends from an end of the first line of perforations 52, obliquely toward the top edge 46, approaching closely

thereto. A second cut 58 extends from an end of the second line of perforations 54. obliquely toward the top edge 46. approaching closely thereto. The cuts 56. 58 can be a single cut. or two or more cuts separated by one or more connecting pieces 57 of the web. Small nicks 56a, 58a are cut into the top edge 46. aligned with the first and second cuts 56.58 respectively. The nicks assist in directing the teanng to precise locations at the top edge 46.

A first tear off region 60 is defined by the first line of perforations 52. the cut 56. the first side edge 40 and the top edge 46. of the bag body 26. A second tear off region 62 is defined by the second line of perforations 54, the second cut 58. the second side edge 42 and the top edge 46. of the bag body 26. Within the first tear off region a unitizing region 66 is formed through the stack 20. substantially perpendicularly to the plane of the back wall 32. A second unitizing region 68 is formed within the second tear off region 62 and through the stack 20. substantially perpendicularly to the plane of the back wall 32. The first and second unitizing regions 66, 68 are formed by penetrating the stack 20 with a hot pin, which forms a hole through the stack and melt-fuses together the bags 24 within the regions 66.68. The holes formed within the regions 66.

68 can be made large enough to subsequently receive rods for guiding or supporting the stack.

Wicketing holes 70, 72. and/or pin holes 74. 76, can be located within the panel 36 which are utilized as described in U. S. Patent 4.699,607. The wicketing holes 70.72 and/or the pin holes 74, 76 act in conjunction with posts and/or sharpened pins to align bags during stack formation. Subsequently, the wicketing holes 70. 72 can receive posts or rods to guide and/or support the stack and allow individual bags to be torn from

the stack. Slits 70a. 72a are provided between the holes 70.72 and the top edge 46 of the bag to assist in orderly tearing off of bags from the stack. Nicks 70b, 72b into the edge 46. can De provided aligned with the slits 70a. 72a respectively.

It is an advantageous aspect of the invention that the line ot perforations 52.54 are perpendicular to the tear off or pull direction F when a user or automated equipment is separating a bag 24 from the stack 20. In this way, maximum tensile stress is exerted on residual web material along the perforated lines 52, 54. The shear regions are minimized due to the extensive cuts 56.58 extending upwardly to the to edge 46 FIGURE 2 illustrates a second embodiment of the invention. In this embodiment. shaped cuts 74.76 extend from ends of the first lines of perforation 52. 54 respectively to the top edge 46. The shaped cuts 74. 76 include an arcuate region 74a.

76a extending into a straight region 74b, 76b respectively. As in the first embodiment. nicks 56a. 56b are aligned with the cuts 74.76, respectively. The lines of perforation 52, 54 and the cuts 74, 76, together with the bag edges 40. 42 and the top edge 46. define substantially rectangular tear off regions 80, 82. The unitizing regions 66.68 are located within the tear off regions 80, 82. Also located within the tear off regions 80. 82 are wicket stacking holes 84. 86 respectively. Stacking via sharpened pins which form pin stacking holes 74.76 into the sheets can also be utilized. Posts can be projected through the holes 74. 76 to allow for bag dispensing in a bag filling operation. Each bag 24 is separated from the tear off regions 80.82 as shown in dashed lines.

It is an advantage of the invention to maximize the dimension X between the tear off regions. and to minimize the dimension Y between the top edge 46 and the mouth 47, to minimize web material waste. The use of the small rectangular tear off regions

80. 82 is advantageous in this regard. The shaped tear off regions 60.62 of FIGURE 1 also advantageously minimizes wasted web material.

FIGURE 3 illustrates an alternate system to block or unitize the stack 20.

According to this embodiment, a flat heated blade is used to form a flat unitizing region 92 on the top edge of the stack 20 of bags 24. In this illustrated embodiment, a wicketing hole 84 is located within the tear off region 80 such as described in FIGURE 2.

FIGURE 4 illustrates an alternate unitizing arrangement. In this arrangement a wicketing hole 94 is also used to unitize the stack. The unitizing wicket hole 94 is located within a tear off region 96 being defined in the same manner as the tear off region 82 of FIGURE 2. However. the separate unitizing region 68 is not required.

Additionally, FIGURE 4 illustrates a semicircular cylinder unitizing region 98. The region 98 can be formed by a hot pin placed on the top edge of the stack 20. The region 98 need not be used with the region 94 as either one of these unitizing regions could be used alone or in combination with other unitizing regions to block a stack of bags.

FIGURE 5 illustrates a further embodiment for unitizing a stack of bags. In this embodiment a plurality of semicircular cylinder regions 102 are formed by hot pins placed on the top edge of the stack 20.

It should be noted that although the wicketing holes in FIGURES 2-5 are located within the tear off regions, the wicketing holes could also be located between the tear off regions such as shown in FIGURE 1. The wicketing holes can be eliminated and the pin receiving holes. formed by sharpened pins of the stack accumulating support.

could be used for aligning the stack of bags before blocking or unitizing. Alternatively, the wicketing holes can be used alone or in conjunction with the sharpened pin- receiving holes. Holes used to unitize the bag stack can also be used for receiving a rod to support the stack, in lieu of wicketing holes. Aiso. although the bags 24 in the stack 20 include a separate flap 36 formed by the back wall 32. such is not a limitation to the invention, as the principles of the invention could be applied to a bag where the front wall and back wall were of a same length, i. e., are coextensive.

Exemplary apparatus to perform the method of the present invention is shown in FIGURE 6, generally designated by the numeral 110. The apparatus as shown would be used to manufacture the bag block shown in FIGURE 2. for example. A web stnp 112 is intermittently advanced by a conventional bag machine (not shown) which may be substantially similar to the machine disclosed in the aforementioned U. S. Patent 4, 451, 249. Feed rolls or draw ro ! ls (not shown) advance the web strip 112 a predetermined amount between a seal bar 114 and a platen roll 116 forming a sheet 118 which is engaged at its longitudinal edges 118a by a pair of transversely aligned arms 120 of a conventional transfer mechanism 122. As a sheet is formed, it is promptly engages by a pair of the radially extending arms 120 and transferred in a generally arcuate path to one of a plurality of stacking plates 124 located at a stacking station S. S. As disclosed in the above-referenced U. S. Patent 4, 451, 249, the stacking plates 124 are carried by a conveyor chain mounted on a frame defining an orbit having an upper reach and a lower reach and driven by an indexing mechanism. The indexing mechanism locates successive blades 124 at the stacking station S. S. for a selected

period of time determined to accumulate a predetermined number of sheet 118 on the respective stacking plates 124.

An area of the web strip 112 upstream from the seal bar 114 is provided. in its central medial zone, identified by dotted lines 112a, with four wicket holes formed by a reciprocating punching device 128 during the period of time when advance of the web strip, in the direction of the arrow A, is arrested. As the web is advanced another increment, the lines of perforations 52,54 and shaped cuts 74, 76 for four bags according to the embodiment of FIGURE 2 are formed by a punch 132 having an interrupted cutting edge. Four bags 24 are formed connected side-to-side and end-to- end with a common corner. as shown more clearly in FIGURE 7. The punch 132 is rigidly connected to a reciprocating rod 134 which is operated to form the lines of perforations 52, 54 and cuts 74. 76 during the period of web repose.

Each web strip 118, defined by the cooperative action of the seal bar 114 and the platen roll 116, accordingly includes, in the medial zone along the leading edge 118b and the trailing edge 118c, two wicket holes 84, 86 located within respective tear off regions 80, 82 as illustrated more clearly in enlarged FIGURE 7. The leading edge 118b and the trailing edge 118c correspond to the side edges 40. 42 of the bags illustrated in FIGURE 2.

Each stacking plate is provided with upwardly extending posts 136 having the upper portion thereof slightly tapered and positioned to receive a succession of sheets impaled thereon as a pair of arms 120 holding a sheet approaches and sweeps by the stacking plate 124 located at the stacking station S. S. In addition to the posts 136 which project through the pre-punched holes. each plate 124 can be provided with

upwardly extending sharpened pins 138 located on either side of an imaginary longitudinal axis L. A. The sharpened pins 138 puncture and penetrate the sheet as it is deposited on the stacking plate 124 and served to firmly retain successive sheets so that a registered stack (meaning that the marginal edges of successive sheets overly each other) is produced.

On depositing a selected number of sheets on a stacking plate 124. the conveyor mounting the plates 124 is indexed, transporting the completed stack to a blocking station B. S. where the sheets are penetrated by heated blades to establish unitizing regions within the tear off regions 80, 82. The apparatus to effect blocking include one or two holders or bars 140 associated with a mechanism such as a pneumatic or hydraulic power cylinder, to forcibly displace the holders 140 toward and away from the stack of sheets. The holders mount blade-like elements 142 which are electrically heated to a temperature to effect fusion of the sheets brought in contact with the surface of the blades 142. On forcibly engaging and penetrating the sheets, the blades or elements 142 produce the unitizing regions described previously in FIGURES 1 through 5 These unitizing regions can be a variety of different shapes and styles as previously described. According to the method of FIGURE 6. at the blocking station all of the sheets are joined along the unitizing regions.

On indexing the blocked sheets to a downstream station, preferably an adjacent downstream station, cutting of the sheets along the longitudinal axis L. A. occurs. The cutting station C. S. comprise a knife 146 mounted in a holder 148 connected to one or more conventional linear actuators operating to automatically. or at the demand of the

operator. to move forward and away from the stacking plate 124 in order to divide the sheets into individual bag blocks as shown in FIGURES 1 through 5.

FIGURES 7 illustrates four bags 24 joined at a central corner to be separated later in the process. which advantageously lays out the necessary wicket holes and perforations for an efficient operation.

Although FIGURE 6 and FIGURE 7 illustrate a machine which forms two blocks of bags simultaneously before being separated into two blocks by the cutter 146, the bags could alternatively be formed by stacking single bag segments. In such a case. a machine similar to that shown in FIGURE 6. but missing one half of the web material on one side of the longitudinal axis L. A.. is used. No cutter 146 is thereby required, and a single draped stack of bags. hung from posts penetrating corner wicket holes and/or sharpened pins is produced.

From the foregoing, it will be observed that numerous variations and modifications may be effected without departing from the spirit and scope of the invention. It is to be understood that no limitation with respect to the specific apparatus illustrated herein is intended or should be inferred. It is, of course. intended to cover by the appended claims all such modifications as fall within the scope of the claims.