A METHOD AND APPARATUS FOR POSITIONING AT LEAST ONE THREAD, BAND OR THE LIKE IN A PRE-DETERMINED PATTERN ON A MATERIAL WEB

Abstract: The present invention relates to a method for positioning at least one thread, band or like element (8) in a pre-determined pattern above a conveyer path (1) with the aid of thread outfeed device (3) having at least one thread outlet device (5). In accordance with the invention, the thread outlet, or each thread outlet, is moved in a simple or a composite rotational path in a plane parallel with the conveyer path, and the path is moved linearly in relation to the rotational axis of the thread outlet. This will cause the thread outlet to move in a spiral-like movement path relative to the conveyer path. The conveyer path has mounted thereon dogging elements (2) which are located within the spiral-like movement path of the thread outlet, such as to enable the thread to be laid out in a pattern determined by the dogging elements. The invention also relates to apparatus for carrying out the method.

Description: The present invention relates to a method and apparatus for positioning at least one elastic tread, band or like element in a pre-determined pattern on a sheet material web for a disposable absorbent article with the aid of a thread outfeed means and a thread outlet. The method and apparatus are particularly intended for laying out elastic treads intended to form the leg and waist elastic of diapers. It is known in the manufacture of so-called disposable diapers to provide the diapers with leg elastic, so that the diaper will fit snugly around the thighs of the wearer. For reasons of manufacture, the elastic threads used to this end in known diapers are placed in mutually parallel relationship. An example of such diapers is found described and illustrated in US-A-3,860,003. These diapers comprise absorbent pads of hour-glass configuration, the narrow central part of which is located centrally between the wearer's legs in use. The use of elastic threads which extend in straight, mutually parrallel lines in the longitudinal direction of the diaper, however, results in chafing against the wearer's skin, on the inward sides of the thighs. It is also known to position the elastication in a V-shape pattern, in which the elastic intersects the absorbent pad in the vicinity of the crotch part of the diaper. Diapers which are provided with this type of elastication will better conform to the contours of the wearer's body than a diaper manufactured in accordance with the aforesaid US patent specification, besides avoiding unpleasant chafing of the wearer's crotch. It is also known to arrange elastic threads in a diamond or network configuration and to produce curved leg elastic similar to that used in tailored leg apparel. One method of producing such elastication is described and illustrated in our Swedish Patent Specification 8406071-4. It is also conceivable to lay elastic threads in a curved path on a continuously advancing web of material, for instance by guiding the thread laying devices electrically, in a backward and forward motion across the web. Such a method of manufacture, incorporating rapid transfer movements, will be complicated, however, particularly in the case of high speed manufacturing lines. Our Swedish Patent Application 8801324-8 teaches a method and apparatus for laying out elastic threads or filaments in a curved path, with the aid of one or more rotating rolls which have peripherally arranged thread-guiding grooves or slots. A method for depositing reinforcement material in the form of threads arranged in a continuous net-like pattern is disclosed in US-A-3 321 348 and US-A-3 829 339. The depositing of the threads in the net-like pattern is obtained by moving carriers or shuttles carrying the thread outlets of a thread outfeed device in a reciprocating movement transversely to the direction of movement of a linearly moving conveyer part, dogging elements being arranged at the edges of the conveyer path and are moving together with said path. EP-A2-0 251 251 discloses a method of producing a pair of tape members spacedly provided and a plurality of elastic strands fixed to the tape members at their opposite ends. By this method an elastic thread is wounded around two conveyer belts spaced from each other with the help of a thread outlet rotated in a plane perpendicular to the plane in which the conveyer belts move. The object of the present invention is to provide a method of the aforesaid kind which will ensure uniform tension in the laid threads; which will enable the threads to be laid with good precision; which can be effected with the aid of only a few moveable components; which will enable the threads to be laid out at high speeds; and which will enable the threads to be laid out in mutually different patterns. This object is achieved in accordance with the invention by means of a method having the characteristic features set forth in Claim 1. Because the thread outlet need only be given a rotational movement, the threads can be laid out at high speeds. This renders the inventive method highly suitable for laying out elastic threads in the manufacture of diapers. Furthermore, the threads can be laid out with great precision, since the precision concerned in the present respect is dependent solely on the accuracy at which the thread dogging elements, thread carriers or like devices are positioned. The invention also relates to apparatus for carrying out the inventive method, the characteristic features of which apparatus are set forth in the following Claim 8. So that the invention will be more readily understood, a number of exemplifying embodiments of the invention will now be described in greater detail with reference to the accompanying drawings, in which Figure 1 is a schematic perspective view of a first embodiment of an inventive apparatus particularly suited for laying out elastic threads on a web of material; Figure 2 illustrated the relative movement path of the thread outlet above the web; Figure 3 is a schematic illustration of a thread pattern in which threads are laid with the aid of two thread outfeed devices which rotate in mutually opposite directions and which form part of the apparatus illustrated in Figure 1; Figures 4A and 4B illustrate the thread pattern obtained when using two thread outfeed devices which rotate in mutually the same direction and which form part of the apparatus illustrated in Figure 1, said apparatus also including thread dogging elements of particular configuration, the profiled section of which dogging elements is shown in Figure 4B; Figure 5 illustrates the configurations of various dogging elements, to the left of the Figure, and a thread pattern obtained when using said elements, to the right of the Figure; Figure 6 illustrates a three-thread pattern which can be employed very advantageously for the purpose of laying out diaper leg and waist elastic; Figure 7 illustrates a second embodiment of inventive apparatus by means of which threads are laid out in a curved pattern; Figure 8 illustrates the relative movement path of a thread outlet located above the material web and included in the apparatus shown in Figure 7; Figure 9 illustrates a second embodiment of an inventive thread outfeed device; Figure 10 illustrates the relative movement path of the thread outlet of Figure 9 above a continuous web; Figure 11 illustrates an application in which a laid-out thread pattern is utilized to wind a thread around a cylindrical object; and Figures 12 and 13 illustrates a third embodiment of an inventive thread outfeed device. Figure 1 illustrates a conveyer path 1, which is driven in the arrowed direction A in some suitable manner, and which may comprise, for instance, a belt-driven endless path. Arranged in the close proximity of the two outer edges of the conveyer path are respective rows of thread dogging elements 2 in the form of pins, studs or like elements, the dogging elements 2 in one row being displaced in relation to the dogging elements in the opposite row, as seen in the direction of path movement. A rotatable thread outfeed device 3 is mounted on a frame, stand or like structure and is positioned such that its rotational axis will intersect the longitudinal symmetry line of the conveyer path. The thread outfeed device includes an outfeed tube 4 having an outlet 5 whose outlet orifice is located at a given distance above the upper surface of the conveyer path and radially outside the rotational axis of the thread outfeed device. The outfeed device is driven for rotation by means of an appropriate mechanism, such as a belt or sprocket wheel 6 and a transmission belt for instance. The thread outfeed device 3 will also preferably be arranged to co-act with an ejector-type thread infeed device, the ejector effect generated by which is operative in blowing a free end of a thread in through the outfeed tube 4, and also with means for preventing slackening of the threads as they leave the outfeed device 3. When the thread outfeed device is intended for use with elastic threads, as in the case of the Figure 1 embodiment, thread tension is preferably achieved with the aid of an unwinding reel or like device, which is driven such that the length of thread unwound from the reel per unit of time will be shorter than the length of thread fed out from the thread outlet. In the case of non-stretchable threads, the slack-preventing means may have the form of a simple friction brake. When laying out inelastic threads, it can also be appropriate to arrange a supplementary thread tensioning device downstream of the thread outlet, particularly in the case of those pattern formations in which not all of the closed loops formed are wound around dogging elements. Figure 1 also shows a material web 7 on which thread 8 exiting from the device 3 is intended to be affixed and which is advanced by means of the conveyer path 1. The manner of operation of the inventive embodiment illustrated in Figure 1 will now be described with reference to Figures 1 and 2. Figure 2 illustrates schematically a relative movement path taken by the thread outlet 5 over the conveyer path 1, when the thread outlet is rotated in the direction of the arrow B. The circular motion performed by the outlet is shown by a broken line in Figure 1. Since during a first half of one revolution (in Figure 1 the half revolution nearest the viewer) the outlet will have a movement component acting in the direction of conveyer path movement and during the second half of said revolution will have a movement component which is counter-directional to the linear movement of said path, movement of the conveyer path relative to the outlet will be greater per unit of time during that half revolution in which the outlet moves against the direction of path movement. The movement path described by the outlet will thus have the form of an extended flat spiral, above the conveyer path, as illustrated schematically in Figure 2. The V-shaped thread pattern shown in Figure 1 is thus obtained by positioning the dogging elements 2 within the spiral-like movement path of the outlet, the dogging elements 2₁, 2₃, 2₅, 2₇ of Figure 1 being placed in the closed loops formed in the spiral-like movement path of the thread outlet. Consequently, when the apparatus of Figure 1 is operating, the thread 8 will be wound one turn around each of the dogging elements 2₁, 2₃, 2₅ and 2₇ on that side of the conveyer path on which the outlet has a movement component in the direction of movement of the conveyer path, and is laid around an outer peripheral part of the opposing dogging elements 2₂, 2₄ and 2₆. As beforementioned, the preferred thread outfeed device 3 is constructed so that the length of thread fed out with each revolution is shorter than the length corresponded by the sum of the distances between the dogging elements 2₁, 2₂ and 2₂, 2₃ respectively. As a result, the elastic thread 8 will be stretched as it is laid out, and will therefore always be brought into abutment with each dogging element that passes the outlet. This will ensure that the thread is unable to jump from a dogging element as a result of being subjected to the influence of external forces generated by vibration, shaking, air-draughts, etc. It will also be understood that it is necessary for the outlet 5 to move more quickly than the conveyer path 1, in order that the outlet has time to pass a dogging element 2₁, 2₃, 2₅ and 2₇. Thus, if it is assumed that a point moves along the line C in Figure 2, it will be seen to be necessary for the outlet to pass through that arcuate part of its movement path which lies beneath the line C in a faster time than the time taken for the conveyer path to move through the distance a , so that a point which is passed by the outlet on the upstream side will also be passed by the outlet on the downstream side, i.e. said point may not move at a speed which will enable said point to leave the movement path of the outlet. Furthermore, the outlet 5 is located slightly above the plane of the conveyer path 1, such that the laid thread 8 will lie immediately above the web 7, but not in contact therewith, so as to enable any variations in thread outfeed speed, rotational speed, conveyer speed, and therewith variation in thread tension, to be equalized in the laid-out thread. The thread laid in the V-shaped pattern shown in Figure 1 is intended to be bonded or likewise affixed to the web 7. This can be effected readily, by pressing the thread against the web with the aid of a roller or like device arranged downstream of the apparatus shown in Figure 1, and by adhesive bonding the thread to the web. The adhesive required herefor may be applied in conjunction with pressing the thread into contact with the web. It is preferred, however, to apply adhesive in a given pattern on the web 7, prior to passing the web to the conveyer path, at a location upstream of the apparatus shown in Figure 1. Subsequent to bonding the threads to the web 7, the threads are clipped from those sections of the conveyer path which protrude beyond the web. Figure 3 illustrates the pattern obtained when a second or further thread outfeed device is mounted in the travel direction, on one side of the first mentioned thread outfeed device 3 illustrated in Figure 1, this second thread outfeed device being arranged to rotate in a direction opposite to the first device. The thread 8₁ laid out by the first device 3 is shown in a full line, whereas the thread 8₂ laid out by the second device 3 is shown in a broken line. Because the second thread outfeed device 3 rotates in a direction opposite to the arrow B, the thread 8₂ will be wound around the dogging elements 2₂, 2₄ and 2₆ instead of around the dogging elements 2₁, 2₃ and 2₅, the thread 8₁ exiting from the first thread outfeed device being wound around these latter dogging elements in the manner aforedescribed. Thus, as will be seen from Figure 3, the threads 8₁ and 8₂ extend parallel with one another within the region of the web 7. Consequently, a V-shaped double elastic can be produced very readily with the aid of the inventive apparatus. Double elastic can also be produced with the aid of two thread outfeed devices which rotate in mutually the same direction, when the dogging elements used have varying height dimensions and when the two threads are caused to exit from respective devices at mutually different heights, i.e. respective thread outlets are positioned at different heights above the conveyer path. Figure 4A illustrates one such thread pattern, and Figure 4B illustrates in side view a dogging element of which the upper part has smaller dimensions than the lower part thereof. The left-hand side of Figure 5 illustrates in side view other dogging element configurations, while shown to the right in Figure 5, from above, are thread patterns 8₁, 8₂ obtained with the aid of such elements. The dogging element shown at the top of the figure can replace the type of dogging element illustrated in Figure 3, whereas the dogging element shown to the bottom of the Figure can replace the type of dogging element illustrated in Figures 4A and 4B. When comparing the centre and bottom views shown in Figure 5, these views being taken from above and illustrating part-patterns produced by thread outfeed devices which rotate in mutually different directions and mutually the same directions respectively, that it is possible with such dogging elements to lay the threads at different distances between mutually parallel threads, in dependence on the directions in which the thread outfeed devices rotate. A study of Figure 5 will also show that the threads can be laid in a trapezoidal configuration, by exchanging the dogging elements 2₂, 2₄, 2₆ of the Figure 1 embodiment with two mutually adjacent and mutually spaced dogging elements in the movement direction of the conconveyer path, provided that these dogging elements are positioned within the movement path of the outlet. Of course, it is also possible to produce regular patterns, the recurring parts of which are formed during more than one revolution of the outlet. Thus, if the dogging element 2₃ is removed from the Figure 1 apparatus, the thread 8 will move parallel with the direction of conveyer path movement, between the dogging elements 2₂ and 2₄ when the outlet 5 has reached the position illustrated in Figure 1, and the thread will thus be laid in a U-shape between the dogging elements 2₁, 2₂, 2₄ and 2₅. If the dogging element 2₄ is removed instead of the dogging element 2₃, the thread 8 will run parallel with the direction of conveyer path movement, between the dogging elements 2₃ and 2₅, in a manner analogous with the former case. Figure 6 illustrates a pattern which is formed by three different threads 8₁, 8₂, 8₃, which have a square-wave-like configuration and which are displaced in phase relative to one another, these threads being shown as a full line thread 8₁, a broken line thread 8₂ and a dotted line thread 8₃. Also shown in dotted, fainter lines in the Figure, is the configuration of the diapers on which the three threads are intended to form leg and waist elastics. The three threads are fed-out at mutually different heights above the web, so that a dogging element or like thread guide which co-acts with solely one of the threads is unable to disturb the laying out of the other threads. Thus, the inventive apparatus enables longitudinal and transverse elastic to be laid out simultaneously, which considerably increases the production rate in comparison with those cases when the longitudinal and transverse elastics must be laid out in separate steps. Furthermore, it is possible, of course, to form patterns from more than three threads, and two conveyer paths can be used when laying out the threads, these paths being later brought together. Figure 7 illustrates another embodiment of inventive apparatus in which two conveyer paths are used and which differs from the apparatus illustrated in Figure 1 by virtue of the fact that the dogging elements are arranged close together in mutually sequential groups 102, 102′, so that the threads will form curved patterns. In other respects, the threads are laid out in a manner analogous with that described with reference to Figures 1 and 2, with the principle difference that more than one dogging element is positioned within the closed loops of the outlet movement path, which means that the length and breadth extension of the dogging element groups must be taken into account when deciding the relationship between the speed of movement of the conveyer path 101 and the rotational speed of the thread outfeed device 103. In order to ensure that the outlet 105 is able to pass on both sides of the dogging element group 102 during rotational movement of the outlet, it is necessary for the outlet of the Figure 7 embodiment to rotate more quickly in relation to the moving conveyer path than the outlet 5 of the Figure 1 embodiment. Figure 8 illustrates schematically the relative movement path of the outlet 105 on the conveyer path 101. As a comparison with Figure 2 will show, the illustrated movement paths of the outlets 5 and 105 have principly the same spiral-like configuration, although the spiral shape described by the outlet 5 is more extended than the spiral-shaped movement path of the outlet 105, due to the differences in rotational speed relative to the speed of conveyer path movement. The dogging element groups 102 have a droplet configuration, with a wider and a narrower part relative to a line which extends parallel with the direction of conveyer movement and which is intersected by the rotational axis of the thread outfeed device 103. The rotational direction of the outlet is preferably chosen so that that part of its revolutionary movement in which the outlet has a movement component in the direction of conveyer movement is located on the same side of the aforesaid line as the broader part of the droplet configuration formed by the dogging element group 102. The apparatus illustrated in Figure 7 is constructed to lay a pattern of two mutually parallel threads and to apply these threads between two material webs 107 and 107′, which are moved past two glue nozzles 111 and 111′ respectively, prior to being brought together and placed on two conveyer paths in the form of belt or chain driven endless belts 101 and 101′. The dogging element groups 102 and 102′, rigidly mounted on the endless belts, pass through the webs such as to project above the webs to a height which will prevent the laid-out threads from coming into contact with the adhesive earlier applied to the web surfaces. The dogging element groups 102 and 102′ will pass successively beneath associated, rotating thread outfeed devices 103 and 103′, which are driven synchronously by a common drive shaft 109. The material webs 102 and 102′ and the overlying threads 108 and 108′ then pass through a press section 110, in which the material webs and the intermediate threads are pressed together and exit from the press section in the form of a double-layer material structure with intermediate double elastic. It is mentioned that the term "overlying" used in conjunction with the outfeed of threads is related to the side of an endless belt on which the threads are laid, this side constituting in this text the upper side, irrespective of whether said side is in reality the upper or the lower side of the belt. As will be seen from Figure 7, the conveyer belts 101 and 101, move in a divergent path subsequent to exiting from the press section, such as to withdraw the dogging elements successively from piercing engagement with the material webs 107 and 107′. The rollers mounted in the press section 110 are recessed in the vicinity of the dogging elements, so as not to damage said elements. In those instances when compression of the parts of the webs lying laterally outside the dogging elements does not induce sufficient compression of intermediate parts such as to achieve positive adhesion of the threads, the rollers may be provided with grooves opposite each pair of dogging elements in the groups 102 and 102′ coinciding in the longitudinal direction of the conveyer path. One conceivable variant is to provide a dogging element construction in which the dogging elements can be withdrawn down into the confines of the conveyer path and biassed towards their working position by means of a spring. It should be mentioned that the aforementioned configuration of press rollers or dogging elements can be applied with all pattern configurations in which dogging elements pierce through the applied material layers, such as in the case of the pattern illustrated in Figure 6 for instance. It should also be mentioned in this respect that the amplitude of the relative movement path of the outlet on the conveyer path can, of course, be varied by changing the radial length of the outfeed tube and by placing the rotational centre of the thread outfeed device to one side of the longitudinal symmetry line of the conveyer path. In the case of the embodiments described hitherto, the thread outlet performs a simple rotating movement. However, those variations in the outlet movement path afforded by varying the relationship between the speed at which the outlet rotates and the speed at which the conveyer path moves, or by changing the radial length of the outfeed tube, will not always suffice in achieving the desired thread lay-out pattern. The possibilities of varying the thread lay-out pattern can be improved, by configuring the thread outfeed device in accordance with the device illustrated schematically from above in Figure 9. In the case of this embodiment, the rotation axle of the outfeed tube 204 is firmly connected to a gear or toothed wheel 209 and axially rigid but rotatably connected to the free end of a rotatable arm 210. The teeth of the toothed wheel 209 co-act with the radially inner teeth of a gear-ring or toothed ring 211, which in the case of the preferred embodiment is stationary. Thus, rotation of the arm 210 in the direction indicated by the arrow D will cause the toothed wheel to rotate about its own axis, by virtue of co-action with the toothed ring, which means, in turn, that the thread outlet will rotate in the direction of the arrow E. When the transmission ratio between toothed ring and toothed wheel is 1:3, the outlet will rotate three times about its own rotational axis for each revolution of the arm 210. Figure 10 illustrates schematically the relative movement path of the thread outlet on a conveyer path moving in the direction of the arrow A. This movement path enables the number of possible pattern configurations to be increased considerably. For example, a thread outfeed device according to Figure 9 can be used with great advantage to form square-wave patterns, such patterns being difficult to achieve with thread outlets which are solely capable of performing simple rotational movements. By varying the transmission ratio between the toothed ring and the toothed wheel and the length of the outfeed tube of the thread outfeed device, the thread outfeed device illustrated in Figure 9 can be used to produce a large number of different thread lay-out patterns. Furthermore, it is also possible in this respect to change the transmission ratio, by rotating the toothed wheel at the same time as the arm 210. As will be understood, the threads laid out by means of the aforedescribed embodiments of the inventive apparatus are not restricted in use to the leg and waist elastic of diapers, and neither need they necessarily be bonded to a flat material layer. Accordingly, an application of the inventive concept in which a thread laid out in a square wave pattern is wound one revolution around a cylindrical object will now be described with reference to Figure 11. In Figure 11 there is shown a conveyer path 301 on which a thread 308 is laid out in a square wave pattern with the aid of a thread outfeed device (not shown) of the kind illustrated in Figure 9. Positioned on the conveyer path above the thread pattern are cylindrical bodies 310, as shown in Figure 11. It will be understood that the cylindrical bodies are illustrated by way of example and that said bodies may have any cross-sectional shape whatsoever. The apparatus illustrated in Figure 1 also includes a gripping device 311 which is intended to co-act with each alternate dogging element 302₁, 302₅ etc. nearest the viewer of Figure 11, in a manner described in more detail hereinafter. The gripping device 311 can be swung through 180°, between a first and a second terminal position, about an axis which lies in the extension of an imaginary line passing through the dogging elements 302₃ and 302₂, and thus has an angle of 45° to the direction of conveyer path movement. The gripping device comprises an arm 312 which in the terminal position shown in Figure 11 extends transversely across the conveyer path and includes two gripping fingers 313, which in the illustrated position lie opposite the dogging element 302₁. In the other terminal position of the gripping device, the arm 312 extends parallel with the direction of conveyer path movement. The conveyer path moves in the direction of the arrow A and the dogging element 302₁ will thus be moved in between the fingers 313. This will cause the arm 312 to be rotated through 180°, from the terminal position shown in Figure 11 to the other terminal position, and the dogging element 302₁, which is constructed so as to be liftable from the conveyer path, will accompany movement of the arm. The dogging element 302₁ will therefore be moved around a semicircular path, as indicated in chain lines in Figure 11, to the position occupied by the dogging element 302₄ in the Figure. At the same time, the dogging element 302₄ is moved together with the conveyer path, and the dogging element 302₁ will thus be located immediately behind the dogging element 302₄ when the arm 312 has reached its other terminal position. The arm 312 is then rotated back to its first terminal position, wherewith the thread 308 can be withdrawn from the dogging element 302₁, by virtue of the fact that at this time point the thread is located beneath the short leg of an L-shaped thread stripper 314. During reverse pivotal movement of the arm 312, the gripping device 311 is moved forwards, parallel with the conveyer path, so that the dogging element 302₁ can be moved back to the same location on the conveyer path. Subsequent hereto, the gripping device is again moved forwards, so that the gripping fingers leave the dogging element 302₁ and the arm 312 is then again rotated to its second terminal position and moved backwards, through the same distance as it was earlier moved forwards. When the whole of the cylinder body has passed the axle connection of the gripping device 311, the arm 312 is again rotated to the position shown in Figure 11, so as to be able to co-act with the dogging element 302₅. When the aforedescribed operation is completed, the thread 308 will thus have been wound through one turn around the cylinder 310. Figures 12 and 13 illustrate schematically an embodiment of a thread outfeed device which is particularly suitable for laying out threads in triangular patterns. In the case of this embodiment, an outfeed tube 404 is carried for rotation by a carrier 410 which can be rotated about a shaft 411 in some suitable manner, for instance by means of a belt transmission. A toothed wheel 412 is rigidly connected to the shaft 411 and engages a toothed wheel 413 which is rigidly connected to a further shaft 414, which in turn is carried for rotation by the carrier arm 410. Mounted on the lower end of the shaft 414 is a toothed wheel 415 which, similar to the toothed wheel 413, is rigidly connected to the shaft 414. This toothed wheel 415 is in engagement with a toothed wheel 416, which is rigidly connected to the outfeed tube 404, such as to rotate said tube relative to the carrier arm 410. The composite movement of the outfeed tube 404 resulting from rotation of the carrier arm 410 in the direction of the arrow E will now be explained with reference to Figure 13, in which the toothed wheels 412, 415 and 416 have been symbolized with circles for the sake of simplicity. Figure 13 shows the outfeed tube 404 and the toothed wheels 412, 415 and 416 in four mutually different, equally spaced positions I-IV during a revolution of the carrier arm 410. The position I is shown in full lines and corresponds to the position of the outfeed tube 404 shown in Figure 12. Rotation of the carrier arm 410 in the direction E will cause the toothed wheel 413 to be rotated by the fixed toothed wheel 412 in an anticlockwise direction in Figures 12 and 13, which in turn means that the toothed wheel 415 will also rotate anticlockwise and therewith cause the toothed wheel 416 and the outfeed tube 404 to rotate clockwise. The gear transmission is therewith so constructed that when the carrier arm 410 is rotated through one quarter of a revolution and has reached the position II in Figure 13, the toothed wheel 416 will also have rotated through one quarter turn. As will best be seen from Figure 13, the outfeed tube 404 has a length such that in the position II the end of the tube will exactly reach the centre of the toothed wheel 412. Subsequent to a further quarter turn of the carrier arm 410, and therewith also of the toothed wheel 416, the outfeed tube is again perpendicular to the longitudinal axis of the path 1 and the end of the tube will extend slightly beyond the movement path of the dogging elements 2. In position III, the outfeed tube, similar to the position II, extends parallel with the longitudinal direction of the web 1. Because of the configuration of the thread outfeed device, the end of the outfeed tube 404 will move in a rectilinear, reciprocating movement path transversely across the conveyer path 1. As will be seen from Figure 12, when laying out threads with the aid of such a device, the thread 8 will not be crossed at any of the dogging elements, as distinct from the case when using the aforedescribed thread outfeed devices, see Figure 1 and Figure 11. The obtainment of uniform thread tension is facilitated by this device. Thus, the invention provides apparatus which enable threads to be laid out at high speeds without the need of complicated thread guides, while still enabling various thread patterns to be readily achieved. Although the method and apparatus according to the invention are primarily intended for laying out threads intended for use as leg and waist elastic in diapers, it will be understood that the invention is not restricted to such use. The invention shall therefore only be limited by the disclosures made in the following claims.

Claims: 1. A method for positioning at least one elastic thread, band or like element (8) in a pre-determined pattern above the surface of a web of sheet material for a disposable absorbent article, such as a diaper, a sanitary napkin or an incontinence guard carried on a conveyer path (1, 101, 301) with the aid of at least one thread outfeed device (3, 103, 203) having a thread outlet (5, 105, 205) including the step of linearly moving the conveyer path, characterized by moving the thread outlet or each thread outlet in a simple or composite rotational movement path in a plane parallel to the conveyer path (1, 101, 301); therewith causing said thread outlet to move in a spiral-like movement path relative to said conveyer path; and by placing thread dogging elements (2) within the spiral-like movement path of the thread outlet, such that the thread (8) will be laid in a pattern determined by said dogging elements. 2. A method according to Claim 1, characterized by maintaining the thread (8) fed from said thread outlet in a tensioned state. 3. A method according to Claim 1 or 2, characterized by rotating two thread outlets (3) positioned sequentially in the relative movement direction of the path (1) in mutually opposite directions such as to provide patterns with double parallel threads. 4. A method according to Claim 1 or 2, characterized by imparting circular motion to the rotational centre of the thread outlet (205) while at the same time rotating the thread outlet about its rotational centre. 5. A method according to any one of the preceding claims, characterized by laying out three or more threads (8₁, 8₂, 8₃) with the aid of separate thread outfeed devices (3, 203) in mutually overlapping U-shaped patterns, such that a sequence of pattern segments comprising a trapezium and a triangle configuration are formed by the laid-out threads; and by adapting the pattern dimensions such that the threads will form the leg and waist elastic of diapers subsequent to having been bonded to a material web which in turn forms a diaper enveloping casing. 6. A method according to any one of the preceding claims in which more than one thread is laid out with the aid of separate thread outfeed devices, characterized by moving the various thread outputs of the thread outfeed devices in mutually different height planes above the conveyer path. 7. A method according to Claim 1, characterized in that two conveyer paths (101, 101′), above each of which at least one thread (108, 108′) is laid out and each of which transport a material web (107, 107′) on which the thread (108, 108′) shall be subsequently affixed, are arranged with the one conveyer path above the other and with said paths sloping towards one another so that in a first direction of movement said paths converge towards one another and then diverge away from one another with the two upper surfaces of the paths facing towards each other; in that the webs are pressed towards each other and towards the threads at the point of intersection of the conveyer paths, such as to bond the threads to the material webs, preferably by gluing; and in that the two combined material webs (101, 101′) with intermediate threads (108, 108′) are separated from the conveyer paths, and moved to a distance from each said path downstrem of the path intersection point, wherewith at least two two-thread patterns are formed between the material webs. 8. Apparatus for positioning at least one elastic thread, band or the like element (8) in a pre-determined pattern above the surface of a web of sheet material for a disposable absorbent article, such as a diaper, a sanitary napkin or an incontinence guard carried on a conveyer path comprising a thread outfeed device (3, 103, 203) located above a continuously moving conveyer path (1, 101, 301), characterized in that the thread outfeed device has a thread outlet (5, 105, 205) which is located radially outwards of the rotational centre of the thread outfeed device; in that a mechanism (6) is provided for rotating the thread outfeed device about is rotational centre; and in that thread dogging elements (2) which project above the conveyer path are arranged in a pre-determined pattern and secured to said conveyer path. 9. Apparatus according to Claim 8, characterized by a mechanism (205, 209-211; 410, 412-416) for rotating the rotational centre of the thread outfeed device. 10. Apparatus according to Claim 8, characterized in that the thread outfeed device (3, 103, 203) includes a thread tensioning device. 11. Apparatus according to Claim 10, characterized in that the dogging elements (2) are arranged in a row along each outer edge of the conveyer path (1) and are displaced relative to one another in the direction of conveyer path movement. 12. Apparatus according to Claim 11, characterized in that two thread outfeed devices (3, 203) are arranged sequentially in the direction of conveyer path movement; and in that said means are driven synchronously in different rotational directions. 13. Apparatus according to Claim 9, characterized in that the rotational axle of the thread outlet (205) is rigidly connected to a toothed wheel (209), the teeth of which co-act with the inner teeth of a toothed ring (211); and in that the toothed wheel is rotatably connected to the free end of an arm (210) which is driven for rotation about an axis extending through the centre of the toothed ring. 14. Apparatus according to Claim 9, characterized in that the rotational axle of the thread outlet (405) is carried for rotation on a rotatable carrier arm (410); that a gear mechanism (412-416) is provided for rotating the thread outlet (404) in a direction opposite to the direction of rotation of the carrier arm. 15. Apparatus according to Claim 8, characterized in that said apparatus includes two conveyer paths (101, 101′) of which one is located above the other with the upper side facing towards the upper side of the other path, and which paths slope towards one another so as to first converge towards one another in the common movement direction and then diverge away from one another; and further includes at least one thread outfeed device (103, 103′) above each said path, means for applying a material web (107, 107′) onto each said conveyer path upstream of respective thread outfeed device, a press section (110) operative to press the material webs and the intermediate threads (108, 108′) together, said press section being located in the junction between the converging and diverging parths of the conveyer paths, and further including means (111 111′) for applying glue to the material webs, and means for conveying the combined material webs (101, 101′) with intermediate threads (108, 108′) from the press section to apparatus for connecting the combined material webs with a further material web on which absorption pads are disposed. 16. Apparatus according to Claim 15, characterized in that the dogging elements on respective conveyer paths (101, 101′) are disposed in a sequence of groups (102, 102′), the dogging elements of each group forming a droplet-like pattern; and in that the distances between the groups and the dimensions of the droplet-shaped patterns are such that the laid-out threads (108, 108′) at their droplet-shaped parts are able to form leg elastic on two opposing sides of mutually sequential diapers subsequent to the combined material webs with intermediate threads having been connected with the further material web carrying absorption pads, and to form transverse elastic for said diapers in the part thereof extending between the groups of dogging elements (102, 102′). 17. Apparatus according to any one of Claims 8-15, characterized in that the dogging elements (2) have a varying cross-section in the direction of their vertical extension. 18. Apparatus according to Claim 17, characterized in that the dogging elements (2) include at least two superposed cylindrical parts, of which the lower of mutually sequential parts has a diameter larger than the upper part. 19. Apparatus according to any one of Claims 8-15, characterized in that each dogging element (2) comprises two cylindrical parts arranged side by side. 20. Apparatus according to Claim 19, characterized in that between said two cylindrical parts of each dogging element is a third cylindrical part which extends vertically above the other two parts. 21. Apparatus according to any one of Claims 17-20, characterized in that each cylindrical part of a dogging element has a thread receiving groove provided peripherally thereon.

Inventors: INDREBO, LEIDULF, JOHANSSON, DAN, PERSSON, LENNART
Applicants: MOELNLYCKE AB
Application year: 1989
Main classification: A61F13
IPC codes: A61F13, B65H81, B65H57, B65H54