the present invention is directed to a method and an apparatus for closing an open slider - operated zipper on a reclosable package . although an embodiment will be hereinafter disclosed that is used in conjunction with a known continuous band sealing unit , the invention is not limited in its application to band sealing operations . the invention may be used in any situation where an open filled package has a slider - operated zipper that needs to be closed , provided that the slider is accessible to the device disclosed below . a known reclosable package or bag 40 of a type that can be closed by the device of the present invention is shown in fig7 . at its top end , the bag 40 has an openable mouth , on the inside of which is an extruded plastic zipper 42 . zipper 42 is opened and closed by manipulation of a slider 20 . the bag shown in fig7 further comprises end stops 52 and 54 for preventing the slider from sliding off the end of the zipper when the slider reaches the closed or fully opened position . such end stops perform dual functions , serving as stops to prevent the slider from going off the end of the zipper and also holding the two zipper profiles together at the ends . the bag 40 may be made from any suitable sheet material or plastic film and comprises opposing wall panels ( only the front panel 44 is visible in fig7 ), which may be secured together at opposite side edges of the bag by seams 46 and 48 ( indicated by dashed lines ). the opposing bottoms of the wall panels may be joined , for example , by means of a seal made in conventional fashion , e . g ., by conduction heat sealing . typically , however , the bottom of the package is formed by a fold 50 in the original packaging film , as seen in fig7 . fig8 depicts a closing end of the slider 20 , with the zipper 42 shown in cross section . the zipper 42 comprises a pair of interlockable closure members 60 and 62 . although rib and groove arrangement is shown for the sake of illustration , the profiles of the closure members may take any form . for example , the zipper may comprise interlocking rib and groove elements or alternating hook - shaped closure elements . the preferred zipper material is polyethylene . the zipper halves further comprise an extension flange 64 connected to the closure member 60 and an extension flange 66 connected to the closure member 62 . although not shown in fig8 , the front and rear wall panels of the bag or pouch can be respectively sealed to the extension flanges , e . g ., by conduction heat sealing . in zippered bags with sliders , as the slider moves across the zipper , the zipper is opened or closed . as shown in fig7 , the slider 14 is slidable along the zipper in a closing direction “ c ”, causing the zipper halves to become engaged , or in an opening direction “ o ”, causing the zipper halves to become disengaged . the slider 20 for opening or closing the reclosable zipper is generally shaped so that the slider straddles the zipper profiles , as seen in fig8 . the slider may be made in multiple parts and welded together or the parts may be constructed to be snapped together . the slider may also be of one - piece construction . the slider can be made using any desired method , such as injection molding . the slider can be molded from any suitable plastic , such as nylon , delrin , polypropylene , polystyrene , acetal , polyketone , polybutylene terephthalate , high - density polyethylene , polycarbonate , or abs . in the case of the particular slider - zipper design depicted in fig8 , as the slider 20 is moved in the opening direction , the side walls of the slider push the rails 68 and 70 of the closure members towards each other , the resulting leverage causes the profiled closure members 60 and 62 to pivot oppositely about a fulcrum 72 and disengage from each other . the male profile of closure member 60 is shaped to readily permit easy disengagement from the female profile of closure member 62 . in the specific embodiment of the invention disclosed herein , the zipper closure device acts on a slider of the type shown in fig8 or any other straddling - type slider , i . e ., sliders without a separating finger . some customers who purchase pre - made slider / zippered pouches and then fill them with product request that the pouches be shipped to them with the slider in the open position . they then manually fill each pouch and set it on a conveyor that carries the pouch to the continuous band sealing unit , where the peel seal is activated . a device is needed for closing the package after it has been filled . a zipper closure device 2 in accordance with one embodiment of the invention is attached to the in - feed side of a continuous band sealing unit 4 , as shown in fig1 . filled packages slide down a chute 6 and land on a moving conveyor belt 8 . the conveyor belt 8 carries the packages in a forward direction . a pair of guide rails 10 a and 10 b , disposed above the conveyor belt 8 , comprise converging portions that form a v shape and mutually parallel portions that form a gap therebetween . the v - shaped portion tracks the pouch into the band sealing unit by guiding the upright portion of the filled package toward the gap between the parallel portions of the guide rails . each guide rail comprises a metal base that holds a plastic rod on the inside . the package contacts the plastic rods only . as the filled package continues to be advanced by the conveyor belt 8 , an intermediate portion of the upright package above the product line enters another gap formed by a pair of mounting plates 12 a and 12 b . the plates are rounded at the entrance of the gap to eliminate snagging of the package as it enters the gap . the mounting plates 12 a and 12 b are disposed in a generally horizontal plane at an elevation higher than that of the guide rails 10 a and 10 b ( see fig2 ). the zipper closure device 2 is mounted on top of the mounting plates 12 a and 12 b , spanning the gap therebetween . at the exit end of the zipper closure device 2 , a zipper guide 30 is provided . the zipper guide 30 comprises a pair of spaced parallel plates comprising a ramped section and a horizontal straight section , the latter providing a pair of parallel straight edges on which the zipper profiles are supported as the package enters the band sealing unit 4 . as seen in fig2 , the gap between the mounting plates 12 a and 12 b overlies the gap between the guide rails 10 a and 10 b . a pair of opposing drive belts 14 a and 14 b are placed with their opposing belt portions vertically disposed in a plane that generally bisects the gap between the mounting plates 12 a and 12 b . each drive belt is supported by the same number of pulleys , the axes of rotation of the pulleys supporting belt 14 a being disposed in a first vertical plane and the axes of rotation of the pulleys supporting belt 14 b being disposed in a second vertical plane , the first and second planes being mutually parallel . as a result , the drive belts 14 a and 14 b form a nip that extends in a vertical plane . the drive belts 14 a and 14 b rotate at the same speed in opposite directions such that the opposing belt portions in the nip move in the forward direction at substantially the same speed as the top portion of the conveyor belt 8 . the zipper closure device 2 has a vertical slot 16 that overlies the gap between the mounting plates 12 a and 12 b . the width of the slot is less than the width of the zipper profile , but wide enough to allow the portion of the package where the zipper flanges lie to pass through . the zipper closure device 2 further comprises a horizontal longitudinal channel 18 that communicates with the top of the vertical slot 16 . the channel 18 has a profile that is shaped to allow the slider to pass through while maintaining the orientation and elevation of the slider substantially constant during slider passage . the slider enters the channel 18 with its opening end leading . the vertical plane of the drive belt nip is generally aligned with the vertical slot 16 of the zipper closure device 2 and overlies the gap between the guide rails 10 a and 10 b . this arrangement provides clearance for the uppermost part of the filled package to pass through , with the slider and zipper profiles passing through the channel 18 while the opposing walls of the package in the area below the zipper profiles passes through the slot 16 and the nip of the drive belts 14 a and 14 b . the drive belts carry the pouch through the zipper closure device 2 and through the band sealing unit 4 . the drive belts can be made of teflon , which is a trade name for a polymer of polytetrafluoroethylene , a tough , heat - resistant fluorocarbon resin . the zipper closure device 2 is shown in greater detail in fig3 - 5 . fig3 is a side view , while fig4 shows the end where the slider ( clipped on the zipper profiles in an open position ) enters and fig5 shows the end where the slider ( clipped on the zipper profiles in the closed position ) exits . each of fig3 - 5 shows a slider 20 inside the channel 18 without the zipper or package walls being depicted to avoid complication . although the profile of the slider depicted in fig4 and 5 differs from the slider profile seen in fig2 in that one leg is longer than the other , the principle of operation of the present invention is the same in either case . as best seen in fig3 , the zipper closure device 2 comprises a converging channel 28 that communicates with the horizontal straight channel 18 for guiding a slider into the straight channel . the converging channel 28 and straight channel 18 form a guideway that may be considered to be a single channel having converging and straight sections . the converging channel section 28 has a cross - sectional area that gradually decreases from the slider insertion end to an intermediate point and the straight channel section 18 , extending from the aforementioned intermediate point to the exit end , has a profile that is substantially constant from the intermediate to a point near the exit end . the embodiment of the zipper closure device 2 shown in fig3 - 5 comprises three parts respectively labeled 2 a , 2 b and 2 c . as best seen in fig4 , lower parts 2 b and 2 c of the guideway are spaced apart at opposing mutually parallel surfaces that form the vertical slot 16 . the slot 16 has a width less than the maximum width of the zipper profile . the upper part 2 a of the guideway comprises three of the surfaces that form the straight channel section 18 , the fourth side of the channel being formed by respective surfaces on the lower parts 2 b and 2 c of the guideway . the surfaces of the converging channel section are distributed over the three parts as seen in fig4 . the end result is four trapezoidal planar surfaces with long bases at the insertion end of the guideway and short bases at the aforementioned intermediate point ( bearing in mind that the fourth trapezoidal surface is bisected by the vertical slot 16 ). the trapezoidal surfaces are disposed such that the decreasing cross - sectional area of the converging channel section is a rectangle . the three parts 2 a - 2 c form a block with channel 28 / 18 and vertical slot 16 each extending along the entire length of the block . in a prototype , the three parts were made of delrin , which is a trade name for a highly crystalline homopolymer acetal resin that is rigid and hard . however , other materials can be used . the converging channel section 28 guides the incoming slider into the straight channel section 18 . the vertical slot 16 holds the uppermost portion of the package upright with the slider oriented with its opening end leading as the package enters the guideway . the package is advanced continuously by the above - described drive belts , causing the slider to travel down the straight channel section 18 . however , the slider is arrested when its leading end abuts a pair of balls 22 ( only one of which is indicated by a dashed circle in fig3 ), which project into the channel section 18 to a degree that further travel of the slider 20 is obstructed . the slider 20 is shown ( by dashed lines ) in fig3 in its arrested position . as shown in fig5 , the upper part 2 a has a pair of coaxial threaded bores 25 a and 25 b that communicate with the straight channel section 18 on opposite sides thereof . respective ball plungers ( the casing 24 of one of which is indicated in fig3 ) are threadably coupled in the threaded bores 25 a and 25 with the balls 22 of the plungers partly projecting into the channel section 18 in direct opposition to each other . alternatively , spring plungers comprising rods with rounded tips that project into the slider guide channel can be utilized . when the zippered portion of the pouch passes through the straight channel section 18 , the slider is in the open position . holding the slider stationary at the ball plungers while the zippered pouch is moved forward by the drive belts and the conveyor belt causes the slider to move in a closing direction relative to the zipper , thereby closing the zipper before the pouch enters the band sealing unit 4 . the structure of one type of ball plunger suitable for use in the present invention is shown in fig6 . the ball plunger comprises a cylindrical casing 24 that has a threaded exterior and a smooth circular bore that is closed at one end . a compression spring 26 is installed inside the circular cylindrical bore with one end of the spring seated against the closed end of the bore . the other end of the spring pushes against a ball 22 , which is held in the circular cylindrical bore by inwardly tapered distal portions of the casing 24 that form a detect hole . the distal portion of the casing is designed to allow the ball 22 to seat against curved surfaces that prevent the ball from leaving the bore and yet allow a portion of the ball to project through the detent hole of the casing and into the channel 18 , as seen in fig6 . an identical ball plunger is provided on the other side of channel 18 , so that a pair of opposing balls project into the channel and obstruct passage of the slider . however , the balls are retractable provided that sufficient side force is exerted on the balls to cause the springs to compress . the level of side force needed to slide a ball out of its detent hole is a function of how far the spring 26 will be depressed , which depends on how far away from the channel surface the ball projects . this in turn is determined by the position of the casing 24 , which can be adjusted by screwing the casing further into or out of the threaded bore 25 in the guideway . thus , the positions of the ball plungers can be adjusted so that the opposing balls retract to respective non - obstructing positions when the side forces exerted by the slider on the balls are equal to a sufficiently high force ( selected to correspond to a minimum acceptable pull - off resistance ) that does not result in the slider being pulled off the end of the zipper . the force exerted by the slider on the balls is due to the lagging end stop pushing against the closing end of the arrested slider while the pouch continues to advance . when the side forces exerted by the slider on the balls reach the pre - adjusted level without the end stop failing , the balls will be pushed out of the way and the slider will pass through the straight channel section 18 . conversely , if the end stop fails and the slider never exerts a side forces equal to the pre - adjusted levels , the zippered portion of the pouch will pass through while the obstructed slider is pulled off the end of the zipper . directly underneath the arrested slider position , the channel 18 communicates with a slider ejection passageway 32 ( see fig3 ) formed in the lower parts 2 b and 2 c of the guideway . the lower parts 2 b and 2 c further comprises respective portions of an inclined slider ejection ramp 34 disposed along a terminal section of the slider ejection passageway . thus a pulled - off slider can be ejected and directed to a catch basin ( not shown ) by the ejection ramp . the device described above enables the closure of filled slider - zippered packages , while at the same testing the pull - off resistance of those sliders . the device is especially well suited for use with slider that do not have a separating finger . the use of spring - loaded obstructions enables the system operator to adjust the amount of force exerted by the slider that will snap the obstructions out of the way . this allows the obstructing fingers or balls to restrain the slider and eject it in the event there is a weak or below minimum pull - off slider end stop . another benefit of the disclosed device is that it increases the accuracy of a more horizontal or level heat seal across the horizontal peel seal strip between the zipper flanges by using the slider as a means of leveling the zippered part of the pouch . the embodiment described above comprises a stationary zipper closure device and a moving package . however , the person skilled in the art will recognize that the concept of the invention will also work if the package is held stationary while the zipper closure device is moved . the principle of the invention is that the slider be obstructed during its transit along a channel . relative movement of the slider and the obstructed channel can be achieved by moving the slider through a stationary channel , by moving the channel over the slider of a stationary package , or by moving the slider and channel in opposite directions with the slider inside the channel . while the invention has been described with reference to various embodiments , it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention . in addition , many modifications may be made to adapt a particular situation to the teachings of the invention without departing from the essential scope thereof . therefore it is intended that the invention not be limited to the particular embodiment disclosed as the best mode contemplated for carrying out this invention , but that the invention will include all embodiments falling within the scope of the appended claims . as used in the claims , the term “ package ” means a container , bag , pouch or other receptacle for objects , material or stuff . a container , bag , pouch or other receptacle is deemed to be a package even if not yet packed with objects , material or stuff . as used in the claims , the term “ spring - loaded plunger ” includes ball plungers , spring plungers , and any other device capable of overcoming and moving in opposition to a spring force in response to application of a side force in excess of a predetermined level . as used in the claims , the term “ block ” encompasses both monolithic bodies and bodies comprising an assembly of parts .