Patent Application
20060207727
The present invention generally relates to apparatus for automatically advancing a length of plastic fastener tape used in reclosable packaging by a predetermined distance.
During the automated manufacture of reclosable bags, successive sections of a continuous length of thermoplastic fastener tape unwound from a supply reel or spool are joined (e.g., by conductive heat sealing) to successive sections of a continuous web of bag making material (e.g., a monolayer of thermoplastic film or a laminate comprising a layer of thermoplastic film). The web-to-fastener tape sealing operation can be performed either intermittently or continuously. Often the fastener tape has sliders inserted thereon, one slider per section, before that section is joined to the bag making material. In the latter event, it is also customary to form one slider end stop structure per section of the fastener tape prior to the latter being joined to the bag making material.
When the fastener tape carries a repeating structural feature (e.g., a slider or slider end stop structure), it is important that that those structural features be accurately placed at regular intervals to ensure that the structural features and the respective pockets or receptacles of the packages or bags are in proper registration. In particular, each slider end stop structure must be correctly aligned with a respective cross seal formed on the package or bag.
There is a continuing need for improvements in automated equipment for ensuring correct registration of slider-carrying fastener tape with precursor packages or bags on a packaging or bag making machine.
The present invention is directed to a machine for repeatedly advancing a length of extruded plastic fastener tape a predetermined distance. In the disclosed embodiments, the starting fastener tape comprises a pair of extruded flanged zipper strips having mutually interlockable closure profiles. In accordance with various embodiments, the fastener tape may be advanced through various fastener processing stations, such as a slider insertion station or an ultrasonic welding station, and toward a take-up roll or toward a fastener application station of a packaging machine, bag machine, form-fill-seal machine, or other similar types of machinery.
One aspect of the invention is an apparatus comprising: a fixed support frame comprising a straight rail; an indexing gripper assembly that is slidably mounted to the rail for linear motion therealong; a stationary gripper assembly that is mounted to the support frame; an indexing drive mechanism for moving the indexing gripper assembly linearly between first and second positions along the rail, the second position being closer to the stationary gripper assembly than the first position is; and a controller programmed to control the indexing and stationary gripper assemblies and the indexing drive mechanism so that the following events occur in the order listed: (a) the indexing gripper assembly is actuated to grip a first section of a length of fastener tape that is substantially straight while the indexing gripper assembly is in the first position; (b) while the indexing gripper assembly is gripping the first section and the stationary gripper assembly is not gripping any section of the length of fastener tape, the indexing drive mechanism is actuated to move the indexing gripper assembly from the first to the second position; (c) while the indexing gripper assembly is in the second position and is gripping the first section of the length of fastener tape, the stationary gripper assembly is actuated to grip a second section of the length of fastener tape that is disposed ahead of the first section; (d) while the stationary gripper assembly is gripping the second section of the length of fastener tape and the indexing gripper assembly is in the second position, the indexing gripper assembly is actuated to release the first section of the length of fastener tape; and (e) while the stationary gripper assembly is gripping the second section and the indexing gripper assembly is not gripping any section of the length of fastener tape, the indexing drive mechanism is actuated to move the indexing gripper assembly from the second to the first position.
Another aspect of the invention is a machine comprising: a first gripper assembly that is movable along a straight line; a second gripper assembly that is stationary during machine operation; means for moving the first gripper assembly between first and second positions along the straight line, the second position being closer to the second gripper assembly than the first position is; and a controller programmed to control the first and second gripper assemblies and the moving means so that the following events occur in the order listed: (a) the first gripper assembly is actuated to grip a first section of a length of fastener tape that is substantially straight while the first gripper assembly is in the first position; (b) while the first gripper assembly is gripping the first section and the second gripper assembly is not gripping any section of the length of fastener tape, the moving means are actuated to move the first gripper assembly from the first to the second position; (c) while the first gripper assembly is in the second position and is gripping the first section of the length of fastener tape, the second gripper assembly is actuated to grip a second section of the length of fastener tape that is disposed ahead of the first section; (d) while the second gripper assembly is gripping the second section of the length of fastener tape and the first gripper assembly is in the second position, the first gripper assembly is actuated to release the first section of the length of fastener tape; and (e) while the second gripper assembly is gripping the second section and the first gripper assembly is not gripping any section of the length of fastener tape, the means are actuated to move the first gripper assembly from the second to the first position.
A further aspect of the invention is a machine for processing a length of fastener tape made of plastic material, comprising: a fixed support frame comprising a straight rail; a first gripper assembly that is slidably mounted to the rail for linear motion therealong, the first gripper assembly comprising a pair of mutually opposing grippers, the fastener tape passing between the grippers of the first gripper assembly; a second gripper assembly that is stationarily mounted to the support frame, the second gripper assembly comprising a pair of mutually opposing grippers, the fastener tape passing between the grippers of the second gripper assembly; an indexing drive mechanism mounted to the support frame for moving the first gripper assembly linearly between first and second positions along the rail, the second position being closer to the stationary gripper assembly than the first position is; a slider insertion device mounted to the support frame, the slider device comprising a pusher that, when extended, moves toward the fastener tape; and a controller programmed for controlling the first and second gripper assemblies, the indexing drive mechanism, and the slider insertion device so that the following events occur: (a) while the second gripper assembly is open, the first gripper assembly is closed and then displaced along the rail from a home position to an away position closer to the second gripper assembly, the grippers of the first gripper assembly gripping a first section of the length of fastener tape; (b) while the first gripper assembly is in the away position, the second gripper assembly is closed and then the first gripper assembly is opened, the grippers of the second gripper assembly gripping a second section of the length of fastener tape; and (c) while the second gripper assembly is closed, the first gripper assembly returns to the home position and the pusher of the slider insertion device pushes a slider onto a third section of the length of fastener tape.
Yet another aspect of the invention is a machine for processing a length of fastener tape made of plastic material, comprising: a fixed support frame comprising a straight rail; a first gripper assembly that is slidably mounted to the rail for linear motion therealong, the first gripper assembly comprising a pair of mutually opposing grippers, the fastener tape passing between the grippers of the first gripper assembly; a second gripper assembly that is stationarily mounted to the support frame, the second gripper assembly comprising a pair of mutually opposing grippers, the fastener tape passing between the grippers of the second gripper assembly; an indexing drive mechanism mounted to the support frame for moving the first gripper assembly linearly between first and second positions along the rail, the second position being closer to the stationary gripper assembly than the first position is; a shaping device a slider insertion device mounted to the support frame, the shaping device comprising a component that, when extended, moves toward the fastener tape, the shaping device being capable of shaping or otherwise deforming the fastener tape; and a controller programmed for controlling the first and second gripper assemblies, the indexing drive mechanism, and the shaping device so that the following events occur: (a) while the second gripper assembly is open, the first gripper assembly is closed and then displaced along the rail from a home position to an away position closer to the second gripper assembly, the grippers of the first gripper assembly gripping a first section of the length of fastener tape; (b) while the first gripper assembly is in the away position, the second gripper assembly is closed and then the first gripper assembly is opened, the grippers of the second gripper assembly gripping a second section of the length of fastener tape; and (c) while the second gripper assembly is closed, the first gripper assembly returns to the home position and the shaping device shapes or otherwise deforms a third section of the length of fastener tape.
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.
An apparatus for repeatedly advancing a length of straight fastener tape by a predetermined distance in accordance with one embodiment of the invention is depicted in
As best seen in
Each of the gripper assemblies 4 and 8 comprises a respective pair of gripper arms that are linked to move equal distances in opposite directions. As seen in
Similarly, the stationary gripper assembly 8 comprises a pair of oppositely moving gripper arms 58 and 60. When the gripper assembly 8 is in a closed state, respective gripper pads on the gripper arms 58 and 60 grip a second section of the length of straight fastener tape, the second section being disposed ahead or forward of the first section. The gripper arms 58 and 60 are actuated by a double-acting parallel motion air cylinder 56 (partly hidden behind gripper arms 58 and 60 in
Each of the parallel motion cylinders 26 and 56 houses a respective piston that can be moved in one direction by supplying compressed air to one of two intake ports on the cylinder (e.g., one of ports 36 and 38 of air cylinder 26, as seen in
Each parallel motion cylinder is mounted to a respective carriage by means of a rigid support structure. As seen in
As previously described, the apparatus depicted in
At the start of the work cycle, the controller causes a double-acting parallel motion air cylinder 26 to extend its piston rod (not shown in the drawings), e.g., by activating a solenoid that, in turn, actuates a valve that connects one of the ports 36 and 38 (seen in
In the next phase of the work cycle, the controller causes a double-acting air cylinder 56 (see
With the stationary gripper assembly 8 open and the indexing gripper assembly 4 still gripping the first section of the length of fastener tape, the controller causes the servomotor 18 to drive the lead screw 16 to rotate a predetermined number of revolutions in a direction that moves the indexing gripper assembly 4 from its home position to an away or forward position. While the indexing gripper assembly 4 moves forward (leftward in
While the indexing gripper assembly 4 is in the away position and still gripping the first section of the length of fastener tape, the controller causes the double-acting air cylinder 56 (see
While the stationary gripper assembly 8 is gripping the third section of the length of fastener tape and the indexing gripper assembly 4 is in the away position, the controller causes the double-acting air cylinder 26 (see
With the stationary gripper assembly 8 closed and the indexing gripper assembly 4 open, in the next phase of the work cycle the controller causes the servomotor 18 to drive the lead screw 16 to rotate the same predetermined number of revolutions, but this time in a direction that moves the indexing gripper assembly 4 from its away position back to its home position. While the indexing gripper assembly 4 moves rearward (rightward in
The steps described in the preceding six paragraphs are then repeated for the next work cycle, starting with activating the indexing gripper assembly 4 to grip a fourth section of the length of fastener tape. The leading edge of the fourth section of the length of fastener tape will be located to the rear of the leading edge of the first section, separated by a distance equal to the return stroke of the carriage of the indexing gripper assembly. Each time the indexing gripper assembly, while gripping the length of fastener tape, travels from the home to the away position, the length of fastener tape will be pulled forward the same predetermined distance. That same predetermined distance typical corresponds to the width of a single package.
In accordance with one application, the fastener tape advancing apparatus depicted in
One embodiment of a fastener tape processing machine of the type described in the preceding paragraph is generally depicted
An ultrasonic welding assembly 72 is disposed downstream of the guide roll 70. During each dwell time, the plastic zipper strips are softened (or melted) and shaped by the ultrasonic welding assembly in a respective zone. The ultrasonically welded plastic material of the respective zipper strips is shaped to form slider end stop structure in each zone upon cooling. The deformed portions of the zipper strips are also fused together in each zone. Each slider end stop structure will form back-to-back slider end stops when the end stop structure is cut during package formation. The ultrasonic welding assembly 72 may comprise an ultrasonic horn and an opposing anvil (not shown in
The ultrasonically welded and shaped portion of fastener tape is then advanced to the next station, comprising a conventional slider insertion device 74 that inserts a respective slider onto each package-length section of fastener tape during each dwell time. Each slider is inserted adjacent a respective slider end stop structure on the continuous fastener tape. The slider insertion device comprises a reciprocating pusher that is alternately extended and retracted by an air cylinder (not shown in
During each dwell time, the fastener tape is gripped by a clamp 88, so that the unwound length of fastener tape spanning the distance between guide roll 70 and clamp 78 is stationary during ultrasonic welding and slider insertion. The clamp 78 may comprise components that are functionally equivalent or similar to the components of the stationary gripper assembly previously described with reference to
At the end of each dwell time, the fastener tape is gripped by a grip-and-pull mechanism 76 and then released by the clamp 78. Also, the ultrasonic horn or anvil or both are retracted and the pusher of the slider inserter is retracted, so that the length of fastener tape is free to advance except where the fastener tape is being gripped by the grip-and-pull mechanism 76. Then the grip-and-pull mechanism 76 is operated to pull the unwound length of fastener tape (ultrasonically stomped and carrying sliders) forward one package length. The most recently inserted slider leaves the slider insertion zone and the most recently formed slider end stop structure is moved from the ultrasonic welding station to the slider insertion zone. The clamp 78 is then closed again, following which the grip-and-pull mechanism is opened and returned to its home position. The grip-and-pull mechanism 76 may comprise components that are functionally equivalent or similar to the components of the indexing gripper assembly previously described with reference to
The length of ultrasonically stomped thermoplastic fastener tape with inserted sliders is then wound on a powered take-up reel 82 and passed through a dancer assembly comprising a weighted dancer roller 80 that is supported on a shaft, which shaft is freely vertically displaceable (as indicated by the double-headed arrow in
All of the foregoing automated steps performed by the apparatus depicted in
Referring now to
During a first phase of each work cycle, the PLC 98 causes the stationary gripper assembly 8 to close. During a second phase, the PLC causes the indexing gripper assembly 4 to open. While the stationary gripper assembly 8 is closed and the indexing gripper assembly 4 is open, the PLC sends control signals to the servomotor 18 that cause the lead screw 16 to rotate in a direction that retracts the indexing gripper assembly 4 from an away position to a home position. During this third phase of the work cycle, the PLC causes the air cylinder 86 to extend the activated ultrasonic horn 88 until it contacts the fastener tape and also causes the air cylinder 90 to extend the pusher 92 so that a slider is pushed onto the fastener tape. The duration of this third phase must be long enough to allow the ultrasonic stomping operation to be completed. During a fourth phase of the work cycle, the PLC 98 causes the indexing gripper assembly 4 to close and then causes the stationary gripper assembly 8 to open. The PLC also causes the horn 88 and the pusher 92 to retract. During a fifth phase of the work cycle, the PLC sends control signals to the servomotor 18 that cause the lead screw 16 to rotate in a direction that extends the closed indexing gripper assembly 4 from the home position to the away position, pulling the length of slider-carrying fastener tape forward one package length. Then the stationary gripper assembly 8 is again closed to start the next work cycle during which another slider will be inserted and another slider end stop structure will be formed. The PLC may also be programmed to control motors (not shown in
Hydraulic cylinders can be employed as actuators in place of air, i.e., pneumatic, cylinders. A person skilled in the art of machinery design will readily appreciate that displacing means other than a cylinder can be used to displace the various components, such as the horn of the ultrasonic welding assembly and the pusher of the slider inserter. For the sake of illustration, such mechanical displacement devices include rack and pinion arrangements or lead screw/coupling nut assemblies, rotation of the pinion or lead screw being driven by an electric motor.
The fastener tape advancing apparatus disclosed herein may also be used in conjunction with a packaging machine or a bag making machine. A second application of the present invention will now be described in which the slider-carrying fastener tape is advanced toward a bag making machine instead of a take-up reel, passing through a drag sealer on its way to the bag making machine. The drag sealer (described in detail later with reference to
One embodiment of a system of the type described in the preceding paragraph is shown in part in
Again, all operations of the components mentioned in the preceding paragraph may be controlled by a PLC, as previously described with reference to
Still referring to
In accordance with the embodiment partly depicted in
After passing through the accumulator (shown in
The folded web 102 and the fastener tape 66 are then advanced together through the drag sealer 94, which is shown as being a vertical sealing apparatus comprising a first pair of mutually opposing heated sealing bars 112a and 112b and a second pair of mutually opposing heated sealing bars 114a and 114b. The sealing bars 112a and 112b are displaceable away from each other, as are the sealing bars 114a and 114b. Sealing of the fastener tape to the folded web of bag making film occurs while the sealing bars are in their respective extended (toward each other) positions. The sealing bars are retracted (away from each other) as needed, e.g., during threading of the web and tape through the sealing apparatus prior to startup.
As the folded web 102 with inserted fastener tape 66 advances vertically and continuously between the opposing sets of sealing bars, the respective zipper flanges of the fastener tape are sealed to the opposing edges of the bag making film, thereby continuously attaching incoming sections of the moving fastener tape to adjoining sections of the moving web. The sealing is accomplished by electrically heating the sealing bars, the heat being conducted through respective endless barrier strips 116a and 116b made of Teflon or similar material, which circulate on respective sets of rollers. Teflon barrier strip 116a passes between one side of the folded web and the sealing bars 112a and 114a, while Teflon barrier strip 116b passes between the other side of the folded web and the sealing bars 112b and 114b. In the gaps between the opposing sealing bars, the web and fastener tape are sandwiched between and held together by the Teflon barrier strips 116a and 116b, which move with the web and fastener tape 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 fastener tape pass through the nips of a series of guide rollers respectively positioned in advance of the sealing bars (guide rollers 118a and 118b); in between the sealing bars (guide rollers 119a and 119b); and after the sealing bars (guide rollers 120a and 120b). It should be appreciated that for the sake of illustration, the Teflon barrier strips, the folded web and the sealing bars are shown in
Although the implementation shown in
Typically each sealing bar assembly (not shown in
The fastener tape and folded web that enter the sealing station unjoined, exit the sealing station joined together by permanent seals. The pinch rolls 122 and 124 (which form part of the bag making machine) continue to pull the joined fastener tape and web forward.
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.
