Patent Application
20050015956
This invention generally relates to methods and apparatus for inserting sliders onto zippers for use in reclosable packaging, such as zippered bags or pouches. In particular, the invention relates to slider insertion devices incorporated in machines for making reclosable packages having slider-operated zippers.
Reclosable bags are finding ever-growing acceptance as primary packaging, particularly as packaging for foodstuffs such as cereal, fresh fruit and vegetables, snacks and the like. Such bags provide the consumer with the ability to readily store, in a closed, if not sealed, package any unused portion of the packaged product even after the package is initially opened.
Reclosable bags comprise a receptacle having a mouth with a zipper for opening and closing. In recent years, many zippers have been designed to operate with a slider mounted thereon. As the slider is moved in an opening direction, the slider causes the zipper sections it passes over to open. Conversely, as the slider is moved in a closing direction, the slider causes the zipper sections it passes over to close. Typically, a zipper for a reclosable bag includes a pair of interlockable profiled closure strips that are joined at opposite ends of the bag mouth. The profiles of interlockable plastic zipper parts can take on various configurations, e.g. interlocking rib and groove elements having so-called male and female profiles, interlocking alternating hook-shaped closure elements, etc. Reclosable bags having slider-operated zippers are generally more desirable to consumers than bags having zippers without sliders because the slider eliminates the need for the consumer to align the interlockable zipper profiles before causing those profiles to engage.
In one type of slider-operated zipper assembly, the slider straddles the zipper and has a separating finger or plow in the middle or at one end that is inserted between the zipper profiles to force them apart as the slider is moved along the zipper in an opening direction. The other end of the slider is sufficiently narrow to force the zipper profiles into engagement and close the zipper when the slider is moved along the zipper in a closing direction.
In the past, many interlocking closure strips were formed integrally with the bag making film, for example, by extruding the bag making film with the closure strips formed on the film. Such constructions, however, were limited by the conditions required to extrude both the film and zipper together. To avoid such limitations, many bag designs entail separate extrusion of the closure strips, which are subsequently joined to the bag making film, for example, by conduction heat sealing. These separate closure strips typically have flanges extending therefrom in such a way that the flanges can be joined to bag making film in order to attach the closure strips to the film. Until recently, slider-operated, separately extruded zippers used flange-type constructions.
An alternative zipper design is the so-called flangeless or string zipper, which has substantially no flange portion above or below the interlockable closure profiles. In the case of a string zipper, the bag making film is joined to the backs of the bases of the closure strips. String zippers can be produced at much greater speeds, allow much greater footage to be wound on a spool, thereby requiring less set-up time, and use less material than flanged zippers, enabling a substantial reduction in the cost of manufacture and processing.
Recently, slider-operated, separately extruded zippers that do not use flange-type constructions have been disclosed. U.S. patent application Ser. No. 10/367,450 discloses a reclosable bag in which respective marginal portions of the bag film are sealed to the backs of respective flangeless zipper strips. The resulting string zipper is actuated by means of a straddling-type slider having a plow that separates the zipper strips during opening. U.S. patent application Ser. No. 10/436,433 discloses methods and apparatus for manufacturing reclosable bags having slider-actuated string zippers, including methods and apparatus for inserting sliders with plows on string zippers. These methods and apparatus may also have application for inserting sliders with plows on flanged zippers or zippers that have been coextruded with the bag.
When inserting a slider having a plow on a zipper, the zipper section where the slider is inserted must be maintained in an open state to allow the slider plow to project between the zipper profiles, but at the same time the side walls of the slider must be able to pass over and straddle the zipper profiles. However, difficulties arise when one attempts to insert the closing end of a slider over an open zipper using an automated insertion device.
There is a continuing need for improved methods and apparatus for automated insertion of sliders with plows on zippers.
The present invention is directed to methods and apparatus for automated insertion of sliders on zippers. Although the disclosed embodiments insert sliders on string zippers joined to bag making film, the invention also has application in the manufacture of reclosable slider bags having a flanged zipper attached to the bag making film or slider bags wherein the zipper and bag making film are co-extruded. Furthermore, the invention has separate application in cases where sliders need to be pre-loaded onto flanged zipper material before attachment to of the zipper flanges to bag making film.
One aspect of the invention is an apparatus comprising: a pusher movable from a retracted position to an extended position for inserting a slider onto a first section of a zipper comprising mutually interlockable first and second zipper strips; first and second guides disposed on opposite sides of a second section of the zipper; first and second grippers respectively disposed on opposite sides of a third section of the zipper disposed between the first and second sections, each of the first and second grippers being movable between respective extended and retracted positions to grip the zipper when the grippers are in the extended positions and to not grip the zipper when the grippers are not in the extended positions; third and fourth grippers respectively disposed on opposite sides of a fourth section of the zipper, the first sections being disposed between the third and fourth sections, each of the third and fourth grippers being movable between respective extended and retracted positions to grip the zipper when the grippers are in the extended positions and to not grip the zipper when the grippers are not in the extended positions; and a splitter plate disposed between the first and second zipper strips along the second and third sections.
Another aspect of the invention is a slider insertion machine comprising: a pusher movable from a retracted position to an extended position for inserting a slider into a predetermined volume of space and onto a zipper that spans the predetermined volume of space; and first and second clamps respectively disposed on opposite sides of the zipper, each of the first and second clamps being movable between respective extended and retracted positions to clamp the zipper on opposite sides of the predetermined volume of space when the clamps are in the extended positions and to not clamp the zipper when the clamps are not in the extended positions.
A further aspect of the invention is a method of inserting a slider onto continuous zipper material, comprising the following steps: (a) opening a section of zipper material by disengaging first and second zipper strips from each other; (b) clamping a first portion of the first zipper strip against one side of a plate, the first portion of the first zipper strip forming part of the open section of the zipper and being disposed on one side of a slider insertion zone; (c) clamping a first portion of the second zipper strip against an opposite side of the plate, the first portion of the second zipper strip forming part of the open section of the zipper and being disposed on the one side of the slider insertion zone; (d) clamping a second portion of the first zipper strip against a second portion of the second zipper strip, the second portions of the first and second zipper strips forming a closed section of the zipper and being disposed on an opposite side of the slider insertion zone; and (e) inserting a slider onto the zipper in the slider insertion zone, with a plow of the slider being disposed between respective third portions of the first and second zipper strips. Step (e) is performed after steps (a) through (d).
Another aspect of the invention is a slider insertion machine comprising: a stationary splitter plate for opening a section of zipper material by disengaging first and second zipper strips from each other; first means for clamping a first portion of the first zipper strip against one side of the splitter plate, the first portion of the first zipper strip forming part of the open section of the zipper and being disposed on one side of a slider insertion zone; second means for clamping a first portion of the second zipper strip against an opposite side of the splitter plate, the first portion of the second zipper strip forming part of the open section of the zipper and being disposed on the one side of the slider insertion zone; third means for clamping a second portion of the first zipper strip against a second portion of the second zipper strip, the second portions of the first and second zipper strips forming a closed section of the zipper and being disposed on an opposite side of the slider insertion zone; and a pusher for inserting a slider onto the zipper in the slider insertion zone, with a plow of the slider being disposed between respective third portions of the first and second zipper strips.
Yet another aspect of the invention is a method of inserting a slider onto continuous zipper material, comprising the following steps: (a) advancing a section of zipper material past a leading edge of a splitter plate that pries first and second zipper strips of the zipper material apart during advancement; (b) clamping a first portion of the first zipper strip against one side of the splitter plate, the first portion of the first zipper strip being disposed on one side of a slider insertion zone; (c) clamping a first portion of the second zipper strip against an opposite side of the splitter plate, the first portion of the second zipper strip being disposed on the one side of the slider insertion zone; (d) closing a portion of the zipper comprising a second portion of the first zipper strip and a second portion of the second zipper strip, the second portions of the first and second zipper strips being disposed on an opposite side of the slider insertion zone; and (e) inserting a slider onto the zipper in the slider insertion zone, with a plow of the slider being disposed between respective third portions of the first and second zipper strips. Steps (b) through (e) are performed during a dwell time after step (a), and step (e) is performed after steps (b) through (d).
Other aspects of the invention are disclosed and claimed below.
Reference will now be made to the drawings in which similar elements in different drawings bear the same reference numerals.
A reclosable package or bag comprising a receptacle 2 and a flexible plastic string zipper 4, operated by manipulation of a slider 10, is shown in
Referring to
At its top end, the receptacle 2 has an openable mouth, on the inside of which is an extruded plastic string zipper 4. The string zipper 4 comprises a pair of interlockable zipper parts or closure strips 6 and 8 (best seen in
The string zipper is operated by sliding the slider 10 along the zipper parts. As the slider moves across the zipper, the zipper is opened or closed. As shown in
The bag shown in
Still referring to
The sealing bridge 12 and the base 14 are resiliently flexible self-supporting structures having a thickness greater than the thickness of the bag film. The male closure elements are integrally formed with the base 14, while the female closure elements are integrally formed with the sealing bridge 12. The upper margins of the walls 2a and 2b of the bag are joined to the backs of the sealing bridge 12 and the base 14 respectively, as seen in
The end face of upper edge of the base 14 that carries the male closure elements 20 and 28 is inclined at about a 45° angle to facilitate loading of the slider onto the zipper from above without snagging on a corner of the upper edge. The bottom edge 8 of the base 14 cooperates with a retaining ledge on the slider (to be described later) to increase the slider-pull-off resistance. For the same purpose, a rib 26 is formed on zipper part 6, the rib 26 cooperating with a retaining ledge on the other side of the slider.
In the slider-zipper assembly shown in
The slider 10 also comprises a plow or divider 42 that depends downward from a central portion of the top wall 32 to an elevation below the lowermost portions of each side wall. The plow is disposed between opposing sections of the zipper parts that pass through the tunnel. The tip of the plow 42 is truncated and has rounded edges and flattened corners 46 at opposing ends for facilitating insertion of the plow between the zipper profiles without snagging during automated slider insertion. The plow 42 comprises a beam having a cross-sectional shape that is a rectangle with rounded corners. The axis of the beam is generally perpendicular to the top wall of the slider. As the slider is moved in the opening direction (i.e., with the closing end leading), the plow 42 pries the impinging sections of zipper parts 6 and 8 apart.
In the embodiment depicted in
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, polypropylene, polystyrene, acetal, polyketone, polybutylene terephthalate, high-density polyethylene, polycarbonate, or ABS.
Improved slider designs are disclosed in U.S patent application Ser. No. 10/412,438, entitled “Molded Sliders for Actuating Zippers of Reclosable Packages”. In one such design, the each retaining ledge on the interior surface of the slider side walls is replaced by a pair of retaining teeth spaced apart at opposite ends of the slider. These improved sliders can be inserted on zippers using the same equipment disclosed herein.
Reclosable packages of the type having a slider with a plow can be manufactured on an automatic production line.
The operations performed continuously during continuous advancement include: unwinding a continuous web of packaging film from a reel; folding the web of film at a folding board; sealing a string zipper to opposing portions of the folded web; and trimming excess film by cutting the film at an elevation above the zipper-film seals.
String zipper material 72, comprising a pair of interlocked continuous flangeless zipper strips, is unwound from a reel (not shown), fed at an angle (not shown) between the upper portions of the legs of the folded web 70, and guided into a position (shown in
The zipper sealing station is conventional apparatus and is described hereinafter only briefly. As the folded web 70 with inserted string zipper 4 advances continuously between the opposing sets of sealing bars 74, the respective zipper strips have their backs sealed to the opposing upper marginal portions of the bag making film, thereby continuously attaching incoming sections of the moving string zipper to adjoining sections of the moving web. The sealing is accomplished by electrically heating the sealing bars 74, the heat being conducted through respective endless barrier strips (not shown) made of Teflon or similar material, which circulate on respective sets of rollers (not shown). Each Teflon barrier strips passes between a respective side of the folded web and a respective sealing bar in the gaps between the opposing sealing bars. The web and string zipper are sandwiched between and held together by the Teflon barrier strips, which move with the web and zipper and prevent the bag making film from sticking against the stationary heated sealing bars during conduction heat sealing. The Teflon barrier strips and intervening web and zipper pass through the nips of a series of guide rollers (not shown).
Downstream from the zipper sealing station, the excess film at the web edges and adjacent the string zipper strips is continuously trimmed by a pair of stationary knives 78 (only one of which is visible in
The trimmed zipper-film assembly then wends its way through a conventional dancer assembly (not shown), which converts the continuous advancement of the film into intermittent advancement of the film. In the intermittent advancement phase, the zipper-film assembly is moved one package increment and then stopped for a period of time, i.e., the dwell time. This cycle is repeated periodically.
In accordance with an alternative embodiment of the automated production line disclosed above, the web of film material and the string zippers could be moved intermittently through the section depicted in
Referring to
In accordance with the preferred embodiment of the invention shown in
As the zipper-film assembly is pulled in the machine direction through the bag making machine (by conventional means not shown), the grooves 92, 94 and the upper and lower guides 84, 86 (best seen in
Referring again to
Systems for transporting sliders to a slider insertion device are disclosed in U.S. patent application Ser. No. 10/106,687 (incorporated by reference herein) filed on Mar. 25, 2002 and entitled “System for Transporting Sliders for Zipper Bags”. That application discloses feeding sliders into a slider insertion device by means of a feeder tube that only accepts correctly oriented sliders having an asymmetric profile, i.e., one leg of the slider is longer than the other leg. Similarly, the slider shown in
As shown in
Referring to
The upper clamp 112 is moved between retracted and extended positions by an air cylinder 136 mounted on a cylinder mounting block 128. The upper clamp 112 is mounted to the end of a piston rod 135. The cylinder mounting block 128 has a guide channel 127 for guiding the upper clamp 112 during its transit. Similarly, The lower clamp 114 is moved between retracted and extended positions by an air cylinder 138 mounted on a cylinder mounting block 130. The lower clamp 114 is mounted to the end of a piston rod 137. The cylinder mounting block 130 has a guide channel 129 for guiding the lower clamp 114 during its transit. The cylinder mounting blocks 128 and 130 are fixed to a support frame not shown. The same support frame supports the tunnel 88 and the slider track 90 and the cylinder 100 depicted in
As best seen in
The interior surfaces of the arms of the U-shaped clamps can be mutually parallel and separated by a distance slightly greater than the width of the pusher. This enables the interior surfaces of the clamp arms to act as extensions of the sidewalls of the pusher channel. This will provide further confinement and alignment of the clip in the pusher as the pusher extends during slider insertion.
During the same dwell time that a slider is being inserted, a slider end stop structure is being formed on the zipper at an ultrasonic stomping station (not shown) downstream from the slider insertion zone. This slider end stop structure will be bisected later during cutting by a hot knife (not shown) to form two slider end stops, i.e., the end stop at the zipper fully closed slider park position for one package and the end stop at the zipper fully open slider park position for the next package. The end stop structure is typically formed by an ultrasonic stomping assembly comprising a horn and an anvil (not shown in the drawings). The horn transmits sufficient ultrasound wave energy into the plastic zipper material that the material is fused into a structure (e.g., a vertically extending hump) defined by the surfaces of the horn and anvil. The horn and anvil may be of the reciprocating or rotary variety.
As seen in
To facilitate threading of the zipper strips through the separator assembly, the upper and lower guides 84 and 86 can be pivoted (e.g., about 5 degrees) away from the splitter plate 82 to allow the zipper strips to be passed between the splitter plate and the upper and lower guides. Upper guide 84 can be pivoted manually upward after the adjustable handle 142 has been untightened, while lower guide 86 can be pivoted downward (under the force of gravity) after the adjustable handle 144 has been untightened. The splitter plate 82 is independently mounted to a base 140, while the upper and lower guide mounts 84, 86 are pivotably mounted to the base 140. The upper and lower guides are locked in place by tightening of the respective handles 142 and 144. The base 140 is part of the support frame.
As previously mentioned, the extension and retraction of the pusher 98, the upper clamp 112 and the lower clamp 114 are achieved in the disclosed embodiment by means of respective air cylinders 100, 136 and 138, generally represented in
A person skilled in the art of machinery design will readily appreciate that displacing means other than cylinders can be used to displace the clamps and the pusher. Any other known mechanical displacement means can be used. For the sake of illustration, such mechanical displacement devices include a rack and pinion arrangement, rotation of the pinion being driven by an electric motor, or a linear actuator with ball screw driven by an electric motor.
While the invention has been described with reference to preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for members 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 verb “joined” means fused, bonded, sealed, adhered, etc., whether by application of heat and/or pressure, application of ultrasonic energy, application of a layer of adhesive material or bonding agent, interposition of an adhesive or bonding strip, etc.
