Patent Publication Number: US-6654992-B2

Title: Method of applying string to tampon pledgets

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to a method of and apparatus for applying a string to a tampon pledget and more particularly to a method of and apparatus for automatically knotting and attaching strings to tampon pledgets in relatively high speed production. 
     Strings may be attached to tampon pledgets using various methods. Some of these methods may be accomplished manually and others require various apparatus. Many of these apparatus are highly complex, requiring significant initial capital expenditures. Examples of such apparatus include those disclosed in U.S. Pat. No. 4,144,623 issued Mar. 20, 1979, entitled, “Process for the Production of Tampon Blanks”; U.S. Pat. No. 4,490,894 issued Jan. 1, 1985, entitled, “Apparatus for Attaching a Withdrawal Cord to a Tampon”; U.S. Pat. No. 5,566,435 issued Oct. 22, 1996, entitled, “Method of Attaching a Tampon Withdrawal Cord with an Overhand Hitch Knot”; and U.S. Pat. No. 6,213,040B1 issued Apr. 10, 2001, entitled, “Apparatus for High-Speed Lacing of an Article”. The complexity of these apparatus can make maintenance and repair of the apparatus difficult and costly. Thus, there is a need for a relatively simple high speed apparatus and method for attaching strings to tampon pledgets. 
     SUMMARY OF THE INVENTION 
     In general, a method of the present invention is for applying a withdrawal string to a tampon pledget having opposite faces and includes positioning the string to extend across one of said faces of the pledget, said string thereby having a generally central portion on said one face and reaches extending on both sides of the pledget, acting on said reaches pneumatically to form the string into a loop looped around the pledget, securing together the end portions of the reaches in the loop, and moving the secured-together end portions through the pledget thereby bringing part of the loop including the secured-together end portions thereof to extend out from said one face of the pledget. 
     In general, apparatus of the invention includes a string feeder for positioning a string to extend across one of the faces of the pledget, said string thereby having a generally central portion on said one face and reaches extending on both sides of the pledget, a pneumatic system operable on said reaches pneumatically to form the string into a loop looped around the pledget, a knotter for knotting together end portions of the reaches in the loop, and a probe movable to drive the knotted end portion of the loop through the pledget thereby bringing part of the loop including the secured-together end portions thereof to extend out from said one face of the pledget. 
     Other features will be in part apparent and in part pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1-6 are schematics illustrating steps of a method of the present invention; 
     FIG. 7 is a side elevation of a tampon having its withdrawal string as applied according to FIGS. 1-6; 
     FIG. 8 is a front elevation of the tampon of FIG. 7; 
     FIG. 9 is a schematic illustrating apparatus for carrying out the method of the invention; 
     FIG. 10 is a section of the apparatus; 
     FIGS. 11 and 12 are enlarged fragmentary views of section shown in FIG. 10; and 
     FIG. 13 is a perspective of part of the apparatus; 
     FIG. 14 is a partially separated view of the part shown in FIG. 13; and 
     FIG. 15 is a perspective of a knotter component of the apparatus. 
    
    
     Corresponding reference characters indicate corresponding parts throughout the several views of the drawings. 
     DETAILED DESCRIPTION 
     FIGS. 1-6 schematically illustrate a method of the present invention which is applicable to a tampon pledget generally designated by the reference numeral  1 . The pledget  1  is of rectangular parallelepiped (i.e., brick-shaped) form having opposite rectangular faces  3 ,  5 ; sides  7 ,  9  and ends  11 ,  13 . As viewed in FIGS. 1-6, face  3  is the front face, face  5  is the rear or back face. The pledget, which is illustrated in a vertical orientation, has a hole  15  extending between the faces  3 ,  5  centered between its sides  7 ,  9  and located between a center of its length and its lower end  13 . The pledget  1  becomes a tampon when a withdrawal string, generally designated by  17 , is applied to it in accordance with this invention. 
     As illustrated in FIG. 1, the first step in the method of this invention is to position a length of string  17 , which becomes the withdrawal string for a tampon, so it extends laterally across one of the faces, specifically face  3  as shown, of the pledget. So positioned, the string  17 , which may be, for example, about 15.5 inches long, has a generally central portion  19  on the front face  3 , and reaches  21 ,  23  extending outward from both sides  7 ,  9  of the pledget. A conventional pneumatic knotter  25  having a hole  27  for receiving the end portions of the reaches  21 ,  23  is positioned behind the pledget  1 . 
     In accordance with this invention, the reaches  21 ,  23  are acted on pneumatically to form the string  17  into a loop, generally designated by L (FIG.  2 ), looped around the pledget  1 . In one embodiment, the reaches  21 ,  23  are acted on pneumatically by suction to draw them back and thereby form the string  17  into the loop L. The suction is produced by drawing a vacuum behind the pledget  1 , as indicated by the arrows in FIG.  1 . The central portion  19  of the string then becomes the bight of the loop L and the reaches  21 ,  23  become the side reaches of the loop. 
     The end portions of the reaches  21 ,  23  in the loop L (i.e., the rearward ends of the reaches) are secured together by the knotter  25  to form a knot  29  (see FIGS.  5 - 8 ). The knot  29  in the ends of the reaches  21 ,  23  is made by pneumatically pulling them into the knotter, as shown in FIG. 3 for action on the ends by the mechanism of the knotter to tie the ends together. 
     After the ends of the reaches  21 ,  23  of the loop L are knotted, the knotter  25  moves forward from its FIG.  3  position toward the pledget  1  as depicted in FIG.  4 . The knotted end of the loop L remains in the knotter  25  under the influence of the vacuum drawn by the knotter as the knotter moves forward. Then, a probe or needle  31  moves lengthwise above the knotter  25  in line with the hole  15  in the pledget  1  from a rearward or retracted position as illustrated in FIGS. 3 and 4 to a forward or extended position as illustrated in FIG.  5 . The tip  33  of the needle  31  has a notch (e.g, a v-shaped notch or u-shaped notch) for capturing the tied-together reaches  21 ,  23 , pulling the looped string out of the knotter  25 , and threading it through the hole  15 . Finally, the needle  31  and knotter  25  are retracted as indicated by the arrow in FIG. 6, leaving the pledget  1  with the string  17  encircling the pledget and extending from the back face  5  to form a double-strand pendant  35  extending from hole  15  as shown in FIGS. 6-8. 
     FIG. 9 schematically illustrates the apparatus of the present invention for carrying out the above-described method of the invention and reference is made to FIGS. 10-15 for details. As schematically shown in FIG.  9  and detailed in FIGS. 10-14, the apparatus comprises a pledget conveyor, generally designated by  37 , having a series of pledget holders  39  spaced at intervals there around (e.g., thirteen equally-spaced holders). Each holder  39  is formed for holding a pledget  1  with its front face  3  totally exposed and facing outward from the conveyor  37  and the lower part of its back (or rear) face  5  being exposed below the holder. Each holder  39  has a perforated back wall  39   a  and forwardly extending side walls  39   b  (see FIGS.  13  and  14 ), being of such height as to allow for the exposure of the lower part of the back face  5  of the pledget from just above the hole  15  down to its lower end  13 . In one embodiment, the conveyor  37  comprises a circular turret rotatable in a horizontal plane on a central vertical axis A, and will be henceforth referred to as such. Spaced at equal intervals around the turret  37  adjacent its periphery is a series of outwardly opening chambers, each generally designated by  41 . Each chamber  41  has a forward or outer part  43  (see FIG. 14) flaring outward from a rearward or inner part  45  which has an inner end  45   a . Each chamber  41  is bisected by a radius of the turret. Each pledget holder  39  is generally centered on an open end of a respective outer chamber part  43 . A series of anvils  47  (FIG. 9) is spaced at equal intervals around the turret  37  midway between the pledget holders  39  for engagement by a string cutter as will be subsequently described. 
     As noted and more particularly shown in FIG. 14, each pledget holder  39  comprises a generally U-shaped body arranged with its open side facing outwardly for receiving a pledget  1  with the front face  3  of the pledget totally exposed. The walls  39   a ,  39   b  of the holder  39  are short enough and so located as to hold a pledget  1  without covering the hole  15  near the lower end  13  of the pledget. A pledget delivery unit, generally designated by  53  (FIG.  9 ), delivers pledgets  1  to the turret  37  and transfers them to the pledget holders  39  as the holders move with the turret through a first zone Z 1  along the endless (circular) path of the holders. 
     A string feeder, generally designated by  55  (FIG.  9 ), feeds string S to each pledget  1  at a second zone Z 2  along the endless (circular) path of the holders  39 . In one embodiment, the string feeder  55  is the same string feeder as disclosed and claimed in a co-assigned U.S. patent application Ser. No. 10/055,573 of Gregory J. Rajala, filed Oct. 26, 2001, entitled “Feeding String” which is hereby incorporated by reference. Broadly, it comprises a pair of godet rolls  57 ,  59  which feed string S from a supply, specifically a cop  61 , with a venturi  63  for retarding the string upstream from the godet rolls and a venturi  65  for accelerating the string downstream from the godet rolls as the string approaches the turret  37 . The feeder  55  feeds the string S as illustrated to extend across the front face  3  of the pledget  1  traveling on its circular path through zone Z 2 . 
     A string cutter, generally designated by  67  (FIG.  9 ), is operable in a third zone Z 3  along the endless (circular) path to cut the string S to length. The resultant withdrawal string  17  includes a central portion  19  extending across the front face  3  of the pledget  1  and reaches  21 ,  23  extending out from both sides of the pledget. The cutter  67  is a conventional rotary cutter cooperable with the anvils  47 , comprising a rotor  69  having cutting blades  71  spaced there around. A vacuum is drawn in each chamber  41  through vacuum line  72  (FIG. 10) when the chamber has passed through zone Z 3 , thereby holding the cut-off length of string  17  on the periphery of the turret  37  and initiating the drawing back of the reaches  21 ,  23  of the cut-off length of string to form the loop L. This may be referred to as the “looping vacuum”. 
     Each knotter  25  is radially movable in its chamber  41  between a radially retracted position adjacent the inner end  45   a  of the chamber and a radially advanced position. The aforesaid looping vacuum is maintained until the loop L is completely formed and the ends are drawn down into the knotter (in its retracted position) as the chamber  41  rotates further and reaches a fourth zone Z 4 . The vacuum is maintained in the knotter  25  from the time when the loop L is drawn into the chamber  41  until the chamber is well past zone Z 4  (as will be subsequently described). The knotter vacuum draws the ends of the loop L into the knotter  25  through its entry hole  27  and the knotter ties the knot  29 . The knotter  25  is a commercially available item, namely a FALU knotter (which is air-operated) sold by K. Fassbind-Ludwig &amp; Co. AG of Wagen by Jona, Switzerland. 
     Each knotter  25  moves radially with respect to the turret  37  in a radial slot  73  (see FIGS. 10 and 14) formed in the bottom of the respective vacuum chamber  41  between the retracted inner position at the inner end of the slot (in which the knotter  25  is shown at the right of FIG. 10) and the extended outer position at the outer end of the slot (in which the knotter is shown at the left in FIG.  10 ). Each knotter  25  slides on radially extending guide rods  75  beneath the respective vacuum chamber  41  as it moves between its inner and outer positions. The knotters  25  are driven in and out by means generally indicated at  77  comprising a cam follower  79  having rollers  81  engaging an annular cam  83  fixed to a stationary annular plate  85  surrounding axis A under the turret  37  and a link  87  interconnecting the cam follower  79  and the knotter. The cam  83  maintains each knotter  25  in its inner position as the knotter travels from zone Z 1  to zone Z 4 , then moves the knotter radially outward to its outer position as it exits zone Z 4 , and then returns the knotter to its inner position as it travels through zone Z 5  and enters zone Z 6 . 
     A flexible closure  89  extends radially outward from each knotter  25  for covering the slot  73  when the knotter is in its inner (retracted) position so that the vacuum may be maintained in the respective vacuum chamber  41 . The closure  89  slides in a curved recess  91  at the bottom of the chamber  41  when the knotter  25  moves out to its outer (extended) position (as shown at the left in FIG.  10  and in FIG.  11 ). The vacuum system of the apparatus, generally designated by  93 , includes flexible vacuum lines (one of which is designated by  95  at the right in FIG. 10) connected to the respective knotters  25  for creating a vacuum in the entry hole  27  of the knotter to draw the end portions of the reaches  21 ,  23  of the string  17  into the knotter. An actuating mechanism for the knotter (generally designated by  97  in FIG. 11) comprises a trigger  99  which engages a set screw  101  in a ring  103  supporting the outer ends of the guide rods  75  as the knotter  25  moves outward. 
     One needle  31  (i.e., elongate piercing tool) is mounted in each chamber  41  of the turret  37 . Each needle extends radially with respect to the turret  37  through a hole  45   b  in the inner end  45   a  of the respective chamber  41 . Each needle  31  moves radially lengthwise between a retracted position wherein its notched tip  33  is positioned near the inner end  45   a  of the chamber  41  and an extended position wherein the tip extends through the hole  15  of the pledget at the front of the chamber. The needles  31  are cam-controlled so that each occupies its retracted position when traveling from zone Z 1  to Z 4 , then moves out radially with respect to the turret  37  when traveling through a zone Z 5 , and then moves radially inward (i.e., retracted) when moving through zone Z 6 . 
     Each needle  31  is held by a slider  107  driven along a radially extending guide rod  109 . The slider  107  has cam follower rollers  111  which engage an annular cam  113  on the stationary plate  85  for moving the needle  31  between its retracted position (shown at the right in FIG. 10) and its extended position (shown at the left in FIG.  10 ). The slider  107  moves the needle  31  by means of a rack and pinion mechanism indicated at  115 . The cam  113  is formed so each needle  31  occupies its retracted position when travelling from zone Z 1  to zone Z 4 , moves radially outwardly when traveling through zone Z 5 , then back into its retracted position when traveling through zone Z 6 . As the needle moves forward (radially outward) from its retracted position, it captures the knotted end of the loop in the tip  33 , pulling the knotted end of the loop out of the knotter  25 . The needle, with the knotted end of the loop captured by its tip  33 , moves forward so it extends through the hole  15  in the pledget, thereby threading the loop through the hole. Then as the needle  31  retracts when moving through zone Z 6 , it releases the end portion of the loop which was captured by the tip  33 , leaving the end portion behind so the string  17  encircles the pledget, extending from the back face  5  of the pledget through the hole  15  and having the aforesaid double-strand string pendant  35  extending from the hole. 
     When the needles  31  move radially outward from their retracted position in the initial phase of zone Z 5  and progress through zone Z 6  to pierce the pledget  1 , the pledget is held in its holder  39  by endless belts  117  and  119 . Belt  117  has an inner reach  117   a  engaging the upper part of the front face  3  of each pledget  1  as the holders  39  carry them through zones Z 5  and Z 6 . Belt  119 , which is below belt  117 , has lugs  119   a  spaced at intervals on the outside thereof each having a hole therein for receiving the tip of a needle  31 . The lugs  119   a  engage the lower part of the front faces  3  of the pledgets  1  as they move through zones Z 5  and Z 6 . 
     Exiting from zone Z 6 , the now strung pledgets  1  pass through zone Z 7  and are plucked off the turret  37  out of the holders  39  by a vacuum take-off roll  121 , then passed to another vacuum take-off roll  123 , and taken to a downstream conveyor  125 . As each chamber  41  exits from zone Z 7 , ending a cycle, it enters zone Z 1  and another cycle is initiated. 
     The vacuum system may embody various suitable means for timing application of vacuum to the chambers  41  and knotters  25 . For example, conventional programmable vacuum valves may be used. 
     Thus, the invention involves stringing tampon pledgets  1 . Each pledget  1  has a front face  3  and a back face  5  and a hole  15  extending therethrough. The series of pledget holders  39  spaced at intervals around the periphery of the turret  37  are rotated around in a circular path. A pledget  1  is placed in each holder  39  in the first zone Z 1  so the front face  3  of the pledget faces outward. String S is fed to each pledget at the second zone Z 2  farther along the circular path by the string feeder  55 , so a length of the string  17  extends across the front face  3  of the pledget  1  with a central portion  19  on the front face and reaches  21 ,  23  extending out from both sides  7 ,  9  of the pledget. The string is cut at the third zone Z 3  farther along the circular path by the string cutter  67  to provide a length of the string (e.g., a 15.5 inch length). A looping vacuum drawn through line  72  acts on the reaches  21 ,  23  in the fourth zone Z 4  farther along the path to draw them back around the sides  7 ,  9  of the pledget  1  thereby forming the string into the loop L around the pledget extending back into the chamber  41 . The end portions of the reaches  21 ,  23  in the loop L are drawn into the knotter  25  by suction induced by vacuum drawn through line  95  and are knotted together (tied together to form the knot  29 ) in the knotter as the pledget  1  travels through the fifth zone Z 5  farther along the path. Then, in zone Z 6  farther along the path, the respective needle  31  moves radially outward over the knotter  25 , capturing the loop in the tip  33  of the needle and driving the loop through the hole  15  in the pledget. Finally, in the final zone Z 7 , the pledget with the withdrawal string is taken away from the turret  37 , and the process repeats. 
     In view of the above, it will be seen that several objects are achieved and other advantageous results attained. 
     As various changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     When introducing elements of the present invention or various embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.