GB2169588A - Bag stacking apparatus - Google Patents

Abstract

Bags are fed from folder (22) to a vertically orbiting conveyor (30) having partitions (32) defining pockets to accumulate a stack. The partitions may be pivoted to the conveyor and arranged to splay as each pocket passes through the trajectory of bags from the folder (22), the widened pocket entrance helping incoming bags to stack one on top of the other. When a pre-selected number of bags have been stacked, the partitions close to direct incoming bags into the next pocket. <IMAGE>

Description

SPECIFICATION Bag stacking method and apparatus This invention relates to handling thermoplastic bags and more particularly to handling folded bags and organizing them in counted stacks.

Patented prior art relevant to the subject matter of the present invention includes U.S. Patent 3,766,701 to O.H. Besserdich and U.S. Patent 3,709,157 to Donald C. Crawford. Both of these patents, assigned to the assignee of the present invention, disclose bag folding mechanisms which are associated with the subject matter of the present invention.

According to the present invention bag stacking apparatus comprises means for moving a bag receiving and accumulating station; means for discharging a continuous succession of bags to the bag accumulating station, to be received in pockets each defined by spaced upper and lower overlying partitions; means for pivoting the upper partition away from the lower partition to increase the entrance area of the pocket; and means, operable when a pre-selected number of bags have been accumulated in the pocket, for pivoting the upper partition back toward the lower partition so that the next discharged bag is received above the upper partition.

Brief description of the drawings Figure 1 is a diagrammatic perspective of the bag handling system incorporating the principles of the present invention, Figure 2 is also a diagrammatic perspective showing, in greater detail, the stack accumulating pocket conveyor and the stack receiving conveyor, Figure 3 is an elevation, partly in section, of the pocket stack generating conveyor and its particular relation with the discharge of the cross-folder, Figure 4 is an enlarged central section of the pocket conveyor illustrating details of construction of the partitions defining pockets for collecting folded bags, Figure 5 is an enlarged fragment of Figure 4 illustrating the operation of a camming surface for controlling the orientation of a partition as it approaches a collecting station, Figure 6 is a fragmentary elevation illustrating transfer of the stack of folded bags from the vertical conveyor to a horizontal conveyor, Figure 7 is a section taken substantially along the line 7-7 of Figure 6, Figure 8 is an enlarged detail of a folded bag being projected out of the crossfolder to a folded bag accumulating pocket, Figure 9 is an enlarged fragmentary perspective illustrating a stop for limiting movement of the rods defining the partitions of the pockets, and Figure 10 is an elevation of bag stack receiving conveyor.

Brief description of the preferred embodiment The bag stacking and stack handling device incorporating the principles of the present invention, shown in Figure 1, is generally identified by the numeral 20 and it is associated and cooperates with a bag folding device 22 being arranged to sequentially fold a bag 24 along lines 23 transverse to the path indicated by the arrows to produce a double-folded bag 26. The double-folded bag is then cross-folded to produce a completely folded bag 28 propelled, in the direction of the arrow R to a vertically orbiting conveyor structure 30 provided with partitions 32 defining pockets in which a selected number of bags are accumulated while orbiting of the conveyor 30 is in progress.The bag stacks, on arriving at a selected station, are transferred in the direction of the arrow S to another conveyor 34 carrying a plurality of bag stack retaining means 36 (Figure 2). Thereafter the bag stacks are either manually removed and placed in a carton or discharged to an automatic cartoner.

Figure 2 shows further details of the system shown in Figure 1 by diagrammatically illustrating the partitions 32 of the conveyor 30 and its direction of circulation in order to sequentially traverse the cross-conveyor discharge station 38 operating to continually supply folded bags to the partitions 32. Additionally, the general configuration of the bag stack retaining means 36, which takes the form of a U-shaped carrier for receiving a stack of folded bags from the conveyor 30 and maintaining them in separate discrete stacks as the conveyor 30 progresses in the direction indicated by the arrow, is shown.

Referring now to Figure 3 which reveals constructional details of the conveyor structure 30 and its physical relationship with the discharge station 38 of the cross-conveyor, it will be seen that the conveyor 30 is supported by frame structure 40 comprising vertically extending legs 42 secured to mounting plates 44 (only one of which is shown) pivotally supporting, by pin 46, a conveyor frame 48 carrying laterally spaced upper sprockets 50 rotatably mounted on a transverse shaft 52 supported in frame 48. A motor-reducer 54, including an integral clutch-brake, drives chains 56 by means of a sprocket chain 58 extending between the output sprocket 60 of the motor-reducer and a sprocket 62, keyed to a shaft 64, which in turn has a keyed thereon axially spaced sprocket 66 (Figure 4) for driving the chains 56.Sprocket chains 56 are held in tension by spring biased sprockets 68 carried by a bell crank 70 having one of its arms rotably mounting the sprocket 68 and the other connected to a rod 72 carrying a spring 74 having its biasing force adjusted by a nut 76 threaded on the rod 72. The free end of the rod is supported in a bracket 78 affixed to a beam 80 carried by side plates 82 which are part of the conveyor frame structure 48.

The partitions 32 projecting outwardly from the path of the chains 56 are preferably a plurality of laterally aligned bars or rods 84 (Figure 9) projecting from and affixed to a rocker shaft 86 (Figure 4) having its opposite ends pivotally mounted in generally U-shaped shrouding plates 88 carried by and extending between the transverse chains 56.

As illustrated in Figures 5 and 9, the inner sur face of a shrouding plate 88 is provided with a channel defined by an L-shaped bracket 90, in which the chains 56 are disposed. In turn, selected pins of the chain project through, at 92, the bent panel 94 of the shrouding plate 88. The ends of the rocker shaft 86 are formed with a reduced diameter poriton 96 (Figure 9) which is freely fitted within a bore formed in the L-shaped bracket 90, to permit rocking movement of the shaft 86. The surface of the plate 88 has formed therein a plurality of elongated slots 98 through which extend rods 84 fixed to shafts 86. On rocking of shaft 86, the rods 84 are inclined with respect to the plate 88. Figure 8 illustrates a set of rods associated with a plate 88 in the inclined position.

The purpose of inclining the rods 84 will be described hereinafter, but it principally insures creation of a selected number of folded bags in each pocket or cavity defined by bars 84 carried by adjacent rock shaft 86. Normally the rods 84 define a 90 degree angle with the surface of the plate 88.

This orientation is established and maintained by a stop 100 (Figure 9) providing an abuttment surface at 102 limiting rocking motion of the shaft 86. The stop plate 100 is secured to the plate 88 by screw fasteners 104 extending through clearance slots 106 which allow, on loosening of the screws 104, adjustment of the plate 100 so that the inclination of the rods 84 with respect to plate 88 can be adjusted.

Figures 4 and 5 reveal details of construction of a preferred way in which the bars 84 are inclined at a selected point of the orbit defined by the chains 56. Each of the rocker shafts 86 has, at one end thereof, a lever arm 108, rotably mounting at one end, a cam follower roller 110 and is rigidly connected, on a flat of the shaft 86, by a fastener 112. Aspring 114, extending between a bracket 116 mounted on a rearward face of the plates 88 and to a post 118 integral with the lever arm 108, biases the shaft 86 in a clockwise direction, as viewed in Figure 5, so that the rods 84 normally assume the position against the stop surface 102.

The above described arrangement of the rocker shaft 86 and the spring 114 biasing the rods against the stop surface 102 provide means operable when a stack of folded bags is being produced to insure that all of the bags of a stack are properly directed to assume an even edge configuration. Included in such means is a camming rail 120 formed with an incline ramp 122 merging with a straight section 124 being parallel to the path of the chains 56. The camming rail 120 is carried by a shoe 126 fixed to the output rod 128 of a linear actuator 130 whose operation is synchronized by a conventional counter which determines the number of folded bags in a stack. Under normal conditions the actuator maintains the rod 128 extended thereby positioning the camming rail 120 in the full outlined position shown in Figure 5.With this orientation, as a roller 110 encounters the ramp 122 pivotal movement of the shaft 86 against the bias of the springs 114 commences and such pivotal movement is arrested when the cam follower roller encounters and passes along the surface 124. Figure 5 illustrates this action by depicting the rods 84A in the full outlined position and the phantom outline position occurring when the actuator 130 retracts the rod 128. The limit to which the rods can be inclined may be adjusted by loosening fasteners 132 and repositioning the camming rail, which is provided with elongated slots 134, to the position desired.

Accumulation of a bag stack can be commenced when successive sets of rods 84 are located adjacent discharge rolls 136 at the discharge station 38.

Accumulation occurs at a loading station LS and continues until a counter has determined that the stack contains a full compliment of folded bags. In the course of movement, the chains 56, locate a full compliment of folded bags at a transfer unit 138 serving to remove a stack of bags from the rods 84 to the bag stack retaining means 36 carried by the conveyor 34. Transfer unit 138 comprises elongated offset rake-like fingers 140 rigidly attached at 142 to elongate rods 144 clamped to spaced cross-heads 146. A clamping bar 148 (Figure 7), secured to the cross-heads 146 by conventional fasteners 150, are provided with semicircular bores 152 corresponding to semi-circular bores 154 formed in the cross-head 146. In this manner adjustment and a selected spacing of the fingers 140 may be achieved, except that the central finger 140A is retained in the middle of the cross-head 146.As shown in Figure 6, the central finger 140A has an extended portion 155 being pinned to a clevis 156 fixed on the end of the output rod of a linear actuator 158 supported on stationary frame elements 160. The cross-heads 146 are guided for rectilinear reciprocation in guide rails 162 being slotted to receive rollers 164 rotably carried by the cross-heads 146. Each of the shrouding plates carries spaced vertical blocks 163 providing a backstop for the bags and gap through which the upper tapered portion 140B of fingers enter in preparation for transfer.

According to this construction, and with reference to Figure 6, when a stack of folded bags assumes a position adjacent to the upper offset portions of the fingers 140, the stack is transferred to the retaining means 36 by actuating the linear actuator 158 to retract its output rod.

The bag stack receiving conveyor 34, which is shown in Figure 10, is supported at an appropriate elevation by legs 166 which in turn support longitudinal frame members 168 having mounted at one end an idler sprocket 170 and at the other end a drive sprocket 172. A drive unit 174, including a reducer 176 and an integral clutch brake (not shown), effect intermittent driving of the sprocket chain 178, tensioned by an adjustable idler sprocket 180. A shaft 182 on which is fixed the drive sprocket 172 also has mounted thereon a camming device 184 provided with three regularly spaced projecting buttons 186 cooperating, through lever mounted roller 188, to actuate a limit switch LS-3 which in turn through the control circuit operates the clutch unit to intermittently advance the upper reach of the conveyor from right to left as viewed in Figure 10.

Trained around sprockets 170, 172 is a chain 189.

Secured to selected extended pins of the chain 189 are base plates 190 carrying upwardly extending abuttments 192 that collectively define bag stack retaining means 36 serving to retain the bag stack in its stacked position during transit along with upper reach of the chain.

To synchronize the operation of collecting bags in a stack, transferring a completed stack to the conveyor 34 and sequentially pivoting a set of bars 84 at the loading station LS a cam 194, provided with projecting lobes 196, is keyed to the shaft 64 (Figure 3). The cam lobes 196 actuate limit switches LS-1 and LS-2 controlling, respectively, the clutch brake unit incorporated in the motor reducer 54 and operation of the transfer unit 138.

While a variety of controls and limit switches are incorporated to effect synchronization of stack generating and stack transferring, only those control units are shown directly associated with these functions.

The counting unit detecting bags discharged by the cross-folder with the bag folding system includes a conventional scanner connected to a counter located in the main control panel which also may include time delay relays to commence certain functions. Bags ejected to a pocket located adjacent to the discharge rolls 136 are received on the rods 84 located adjacent the discharge rolls.

During the time bags are being collected in a stack the chains 56 are being circulated at a rate so that during the discharge of successive bags the distance traveled is greater than the thickness of a folded bag in order to insure unobstructed travel of a bag in its trajectory. Stated another way, any unobstructed passage or path for incoming bags is established by moving the conveyor chain at a speed sufficient to insure that a previously stacked bag will not obstruct the progress of an incoming bag. Side baffles 145, carried by the frame 48, contribute to directing the folded bags to the loading station LS. When the last bag of a stack has been received movement of the chains 56 is arrested since at this time one of the lobes 196 actuates the limit switch LS-1 deenergizing the clutch and energizing the brake.Substantially concurrently the limit switch LS-2 is closed actuating a valve for admitting pressure fluid to the actuator 158 moving the cross-heads 146 and the transfer fingers 140 from left to right, as viewed in Figures 3 and 6, displacing a stack of folded bags to the bag stack retaining means 36 of the conveyor 34. Although not shown, retraction of the actuator 158 operates another limit switch conditioning the circuit to de-energize the brake and energize the clutch of the motor unit 174 indexing conveyor 34 until limit switch LS-3 is closed thereby de-energizing the clutch and energizing the brake associated with the drive unit 174. In addition to advancing the conveyor 34 the limit switch operated by retraction of the actuator 158 additionally extends the actuator to the location shown in Figure 3.When the bag transferring unit returns to its normal position a limit switch is actuated which in turn operates a valve admitting pressure fluid to the actuator 130 displacing the camming rail 120 to effect raising of the rods 84 which immediately overlie the rods on which a new stack of folded bags will be accumulated. The inclination of the rods serves to insure deflection of all bags into a stack since the receiving area is significantly expanded by inclining the rods as indicated. Concurrently with the actuation of the actuator 130 the clutch brake in the motor drive unit 54 is again conditoned to drive the chains 56 to reestablish movement of the bag receiving pocket defined by successive sets of rods 84.

Accordingly, the stacking device receives a continuous stream of folded bags in pockets defined by successive partitions 32 being positioned adjacent a loading station LS. Timed orientation of the upper portion of a pocket, from an inclined (Figure 8) to a position normal to shrouding plate 88 segregates the folded continuously discharged bags into discrete counted stacks.

Claims (9)

1. A method of stacking bags wherein a pre-selected number of bags are accumulated in stacks in successive pockets defined by partitions articulated on an endless conveyor operating in a substantially vertical plane past means discharging a continuous succession of bags, the conveyor moving so that any given pocket will pass through the trajectory of the discharged bags to accumulate bags one on top of the other until the selected number have been stacked and the pocket has moved out of the bag's trajectory; the bag stack thereafter being transferred from the pocket to another conveyor.

2. A method as claimed in claim 1, wherein the partitions are arranged to pivot to open wider as a given pocket passes through the bag's trajectory to increase the pocket's entrance area and to pivot back to their original position once the pre-selected number of bags has been accumulated.

3. A method as claimed in claim 1 or claim 2, wherein the conveyor is controlled to stop moving whilst a bag stack is being conveyed to said other conveyor.

4. Bag stacking apparatus comprising means for moving a bag receiving and accumulating station; means for discharging a continuous succession of bags to the bag accumulating station, to be received in pockets each defined by spaced upper and lower overlying partitions; means for pivoting the upper partition away from the lower partition to increase the entrance area of the pocket; and means, operable when a pre-selected number of bags have been accumulated in a pocket, for pivoting the upper partition back towards the lower partition so that the next discharged bag is received above the upper partition.

5. Apparatus as claimed in claim 4 and further comprising means for transferring a completed stack of bags from a pocket to a compartment provided with means for retaining the bags in their stacked condition.

6. Apparatus as claimed in claim 4 or claim 5, wherein the moving bag accumulating station comprises a conveyor orbiting in a vertical plane and positioned so that its downwards movement passes adjacent the bag discharging means, the conveyor supporting a series of equi-spaced partitions which are sequentially positioned to receive bags supplied by the discharging means.

7. Apparatus as claimed in claim 6, wherein the partitions each comprise coplanar rods secured at one end to a rocker shaft disposed between lateral chains of the vertically orbiting conveyor, the rods projecting perpendicularly to the plane containing the conveyor chains; means being provided to operate when each rocker shaft approaches the bag discharging means to pivot a rocker shaft to incline the rods carried thereby away from the perpendicular and to pivot the rocker shaft in the opposite direction to return the rods to the perpendicular when a pre-selected number of bags have been accumulated in a preceeding pocket.

8. Apparatus as claimed in any of claims 5 to 7, wherein means are provided to stop movement of the conveyor during operation of the bag stack transfer means.

9. Apparatus as claimed in claim 4 and substantially as described with reference to or as shown by the Drawings.