The invention relates to a method and apparatus for supplying a continuous thread to a filter making machine. Especially, it relates to a method and apparatus for use in the manufacture of smoking articles such as the production of filters for smoking articles.

Known filter making machines allow the insertion of a continuous thread into a filter, which thread may be imbued with flavour. In these machines, bobbins provided with continuous thread need often be replaced, which is performed preferably such that no interruption in thread delivery to the filter making occurs. Depending on the thread used the delivery of the thread has to meet high technical demands in order not break or damage the thread during for example the unwinding of the thread from the bobbin.

Therefore, there is a need for a method and apparatus that enables a reliable continuous supply of thread to a filter making machine.

According to an aspect of the present invention, there is provided a method for supplying a continuous thread to a filter making machine. The method comprises the steps of providing a continuous thread on a bobbin and providing a compensation drum and rotating the compensation drum to supply continuous thread to the filter making machine. The method further comprises the step of guiding the continuous thread from the bobbin via a guide arm to and around the, preferably evenly, rotating compensation drum. Yet further, the method comprises the step of winding a buffer length of continuous thread onto the compensation drum by rotating the guide arm in a direction opposite the rotational direction of the compensation drum. The buffer length is longer than the length of continuous thread which is continuously unwound from the compensation drum and supplied to the filter making machine. A further step of the method comprises reversing the rotational direction of the guide arm. This is done such that the guide arm rotates with the compensation drum, when the buffer length of continuous thread has been wound onto the compensation drum, thereby, unwinding the buffer length of continuous thread from the compensation drum. By this, continuous thread may be continuously provided to the filter making machine.

By providing a compensation drum and winding and unwinding a buffer length of continuous thread onto and from said compensation drum, a continuous supply of thread to a filter making machine or to any other apparatus requiring a continuous supply of thread, may be realized. Even if a supply of thread from a bobbin is interrupted, a supply to the filter making machine may be continuously provided, preferably in an even manner from the compensation drum. Especially, a replacement of a bobbin with a replacement bobbin may be performed without interruption of the supply of thread to the filter making machine and preferably without a variation in a supply speed. By this, a filter making machine may be operated continuously and preferably also at a constant speed. Also a smooth and continuous guiding of a thread may be provided by the apparatus according to the invention and a continuous tensioning of the thread may be realized. These measures are especially suitable or required for thread, which may break easier than a thread made from cellulose acetate tow, such as, for example a thread made of or comprising cellulose fibers, such as paper yarn.

In the method according to the invention, the thread from the bobbin is guided by the guide arm, for example over pulleys arranged at the guide arm. The thread is then wound around the compensation drum. In normal use, that is, when thread is continuously provided from the bobbin, the guide arm is stationary and the thread leaving the guide arm may be wound around the compensation drum. The thread performs for example about one entire turn before being supplied to the filter making machine. By this, an even supply of thread from the compensation drum to the filter making machine is supported. This arrangement may advantageously prevent sudden jerking in the provision of thread from the bobbin that may otherwise tear the thread. The rotational speed of the compensation drum defines, together with the diameter of the compensation drum, the speed the thread is supplied to the filter making machine.

Before a bobbin comes to an end or a supply of thread has to be interrupted, a buffer length of continuous thread is wound onto the compensation drum by the guide arm. This buffer length of continuous thread may be unwound again during interruption of thread supply from the bobbin. An upcoming end of bobbin or interruption in general may be detected, for example, by a laser detection system, which for example detects a variation in diameter of the bobbin. Alternatively, the detection system may keep track of the length of thread that has been dispensed from the bobbin. Other suitable means of detection of the end of the thread on the bobbin are known in the art. By this, the thread consumption may be evaluated and the provision of a compensation buffer length of continuous thread to be wound onto the compensation drum may be initialized. According to the invention, once the creation of a buffer length of continuous thread on the compensation drum is initialized, the guide arm starts to rotate around the compensation drum in a direction opposite the rotational direction of the compensation drum. During the winding action, thread is continuously unwound from the compensation drum with the rotational speed of the compensation drum and supplied to the filter making machine. Due to the opposite rotational direction of the guide arm, as well as due to a preferably higher (opposite) rotational speed of the guide arm than the rotational speed of the compensation drum, a buffer length of continuous thread is wound onto the compensation drum.

According to the invention, in some embodiments, once a desired or predetermined buffer length of continuous thread is reached on the compensation drum, the rotational direction of the guide arm is reversed such that the guide arm is now rotating with the compensation drum. A reversing of the rotational direction of the guide arm may for example be realized by reversing a drive direction of a drive for the guide arm. Preferably, the drive for the guide arm is then synchronized with a drive for the compensation drum such that guide arm and compensation drum rotate at a same speed. However, a reversing may also be achieved by stopping the rotation of the guide arm into the direction opposite the rotational direction of the compensation drum and by engaging the guide arm with the compensation drum. This may for example be done by a latch mechanism. The latch mechanism may be released as soon as the buffer length of continuous thread has been unwound from the compensation drum and normal use shall start again. As soon as the guide arm stops or rotates with the compensation drum, the buffer length of continuous thread that has been wound onto the compensation drum before is now unwound with the rotational speed of the compensation drum. During the time buffered thread unwinds, no thread needs to be supplied to the compensation drum. Therefore, in preferred embodiments of the method according to the invention, the bobbin is replaced while unwinding the buffer length of continuous thread from the compensation drum.

Preferably, a buffer length of continuous thread to be wound on the compensation drum is predetermined. The buffer length may be defined by operation parameters, such as for example, thread thickness, rotational speed of the compensation drum and desired compensation time to be provided by the unwinding of the buffer length of continuous thread. Advantageously, the buffer length of continuous thread is predetermined to compensate for a predetermined time period during which no continuous thread is supplied from the bobbin to the guide arm. By this, the predetermined length wound onto the compensation drum is selected such as on one hand to consider an unwinding of thread from the compensation drum already during winding the buffer length of continuous thread onto the compensation drum. On the other hand the considerations also include the unwinding of the buffer length of continuous thread after the loading of thread by the guide arm has stopped. Preferably, the buffer length is predetermined such that, for example, an exchange of a bobbin and a combining of threads (end of thread from bobbin in use and beginning of thread of replacement bobbin) may be performed, while thread is continuously supplied to the filter making machine, preferably also always supplied at a same speed.

Preferably, an end portion of thread from the bobbin is kept stationary, for example in an inlet of the guide arm, while the buffer length of continuous thread is unwound from the compensation drum. The rotation of the guide arm rotating with the compensation drum enables a fixed position of the end portion of the thread, which is favorable or required for, for example, a connecting of the thread with another thread .

The method according to the invention may further comprise the step of varying the axial position on the compensation drum onto which the buffer length of continuous thread is supplied to the compensation drum. By varying the axial position on the compensation drum where the buffer length is supplied to, the buffer length may be wound along the length of the compensation drum. By this, individual turns of the thread are arranged next to each other and do no not overlap, which facilitates an unwinding. A varying of the axial position is performed during winding the buffer length of continuous thread onto the compensation drum. A varying of the axial position may also be performed during unwinding or after unwinding, for example to perform a more uniform unwinding or to reset apparatus elements.

A varying of the axial position may for example be realized by moving the guide arm, or parts of the guide arm, and the compensation drum relative to each other in the axial direction of the compensation drum. A relative movement performed during unwinding or after unwinding allows for example to move the guide arm or the compensation drum back to its initial position. Preferably, the guide arm is moved relative to the compensation drum. Preferably, a variation in the axial position may be performed by a worm gear to which the guide arm may be connected.

Preferably, the buffer length of continuous thread is wound onto the compensation drum in a single layer.

This may for example be realized by relatively moving guide arm and compensation drum in one direction only, during winding the buffer length onto the compensation drum. A buffer length being wound or provided in a single layer enables a winding and unwinding of the thread at a same time. For example, thread may be unwound at one end of the compensation drum, while at the same time further thread is wound onto the compensation drum at a position versus an opposite end of the compensation drum. A buffer length may in this case be determined by the length and the diameter of the compensation drum.

The method according to the invention may further comprise the step of connecting an end portion of the continuous thread of the bobbin and a beginning of a continuous thread of a replacement bobbin in a connecting means. Preferably, connecting means are operated automatically. An automatic connecting of threads facilitates and may accelerate the supply operation. Preferably, the end portion of the thread from the bobbin and the beginning of the thread of the replacement bobbin are kept stationary upon the connecting step. Connecting may be performed by unraveling of the threads and interconnecting the unraveled ends with each other by support of an air jet or water. In preferred embodiments of the method according to the invention, the two end portions of the threads are arranged next to each other, are provided with an adhesive and are pressed together. The connecting action may be supported by a heat source, for example a hot air jet. Heat may activate an adhesive or may accelerate a drying of the adhesive or both. Preferably, connecting means are arranged next to the shaft for a bobbin. Alternatively or in addition, the two thread ends may be arranged next to each other and attached by winding a string of filamentary material around the overlapping section of the two thread ends. The string of filamentary material may be knotted together to fix the attachment. Alternatively, the string of filamentary material may be glued to the two thread ends to fix the attachment of the two thread ends. The string of filamentary material may be for example cotton, nylon or any other suitable material. Preferably, the string of filamentary material is unwound and cut from a bobbin of string.

Preferably, thread portions comprising a connection are removed after the splicing of the two end portions of thread. This is advantageous as typically such a connection of threads does not fulfill the specification of a thread to be used in a product. For example, the connection comprises an excess amount of thread, an additional string or an adhesive that does not conform with the product specifications.

Continuous thread having been transferred to a filter making machine is inserted into a filter material. A so produced endless filter rod is typically cut into double filter elements, which are then combined with tobacco rods arranged at opposing ends of the double filter element. Preferably, the connection is removed together with a cut filter element. An identification of thread portions comprising connections may be done by appropriate control or sensing means, for example optical detection systems. Preferably, a connection in the filter element is detected shortly before the thread is inserted into the filter material or after insertion. It is for example possible to detect and store a position of a connection in a thread in a control unit. This may, for example, also be the position, where the connection, for example an adhesive bond or a knot, is fabricated. A cut filter element containing the thread portion that has travelled by a distance between connection fabrication and filter cutting position may be removed.

Thread used in the method according to the invention may be a thread as known in the manufacture of filter elements for smoking articles, such as cellulose acetate yarn. Generally, a thread is introduced into a filter material, such as a filter tow and may have a colour different from the colour of the filter material. The thread may also be used to carry a flavourant, such as for example menthol or tobacco flavor. Preferably, the thread used in the method according to the invention comprises cellulose fibers. Preferably, the thread is substantially made of cellulose fibers, possibly including some binders.

Thread made of cellulose fibers is also called paper yarn. Paper yarn may for example be made of recycled cellulose fibers. Preferably, a diameter of paper yarn is in the range of between about 0.3 mm and about 1.8 mm, more preferably in a range between about 0.6 mm and about 1.6 mm, for example between 0.8 mm and 1.4 mm.

As a general rule, whenever the term "about" is used in connection with a particular value throughout this application this is to be understood such that the value following the term "about" does not have to be exactly the particular value due to technical considerations. However, the term "about" used in connection with a particular value is always to be understood to include and also to explicitly disclose the particular value following the term "about".

According to another aspect of the invention there is provided an apparatus for supplying a continuous thread, preferably paper yarn, to a filter making machine. The apparatus comprises a shaft for holding a bobbin of continuous thread and a rotatable compensation drum. The apparatus further comprises a guide arm arranged next to the periphery of the rotatable compensation drum. The guide arm is adapted to be rotatable around the compensation drum. The guide arm is adapted to guide a continuous thread supplied from the bobbin on the shaft to the compensation drum and the apparatus is adapted to supply the continuous thread from the compensation drum to a filter making machine. The apparatus further comprises a drive for rotating the guide arm, preferably for rotating the guide arm at least in the direction opposite the rotational direction of the compensation drum. Yet further, the apparatus comprises a control unit adapted to initialize starting and stopping rotation of the guide arm around the compensation drum. The control unit is also adapted for setting a rotational speed of the guide arm relative to a rotational speed of the compensation drum, such that upon rotation of the guide arm around the compensation drum in the direction opposite the rotational direction of the compensation drum, a buffer length of continuous thread is wound around the compensation drum, and such that the buffer length of continuous thread on the compensation drum is unwound from the compensation drum upon reversing the rotational direction of the guide arm. By reversing the rotational direction, a continuous supply of continuous thread is unwound from the compensation drum to the filter making machine.

The apparatus according to the invention may further comprise a latch mechanism for engaging guide arm and compensation drum such as to make the guide arm to rotate with the compensation drum. By the provision of a latch mechanism and engaging said latch mechanism, the guide arm may automatically be synchronized with the compensation drum in rotational direction and speed. In addition, the drive for the guide arm need only be provided for rotating the guide arm in a rotational direction opposite the rotational direction of the compensation drum. In the non-engaged position of the latch mechanism, the guide arm may be arranged in a stationary position during normal use or may rotate in an opposite direction during the loading step of the buffer length of the continuous thread.

The apparatus according to the invention may comprise a moving device for varying the axial position on the compensation drum onto which the buffer length of continuous thread is supplied to the compensation drum.

Advantages and further aspects of the invention have already been described with reference to the method according to the invention and will therefore not be repeated.

The apparatus according to the invention may comprise mechanical dancers and pulleys for controlling a tightening of and for guiding the continuous thread.

By pulleys and mechanical dancers a controlled guiding of the thread as well as a constant tightening of the thread may be achieved. This is especially favorable when using thread that tends to split or break upon large or irregular tearing or pulling force, such as for example some thread made of cellulose fibers, in particular paper yarn.

The apparatus according to the invention may comprise a replacement shaft for holding a replacement bobbin. Therein the replacement shaft is movable relative to the shaft such as to bring the axis of the first shaft and the axis of the second shaft into alignment with each other.

By providing a movable replacement shaft the replacement shaft may be provided with a replacement bobbin, which may additionally be prepared for use at a location remote from the bobbin in use. Thus, disturbance of the running thread supply process may be minimized. In addition, more space is available for a safe and fast removal of an empty bobbin. An alignment of the shaft and replacement shaft also facilitates a following connecting process, wherein also the shaft may be arranged in a movable manner such as to provide more flexibility in the arrangement of the components of the apparatus. Through an alignment of the two shafts, the end portion of the thread of the bobbin in use and the beginning of the thread of the replacement bobbin may be aligned and especially arranged adjacent to each other, wherein some overlap in a longitudinal thread direction may be achieved. By this, a well-defined connection of the two threads over a portion of the thread may be achieved.

The apparatus according to the invention may further comprise connecting means for connecting two end portions of continuous thread to each other to form a connected continuous thread. Preferably, the connecting means are operated automatically. Connecting means may comprise a compression device for compressing the two end portions of continuous thread to each other. The connecting means may also comprise an applicator for applying an adhesive to the end portions of continuous thread. Preferably, the two end portions are at least slightly compressed before adhesive is applied. Preferably, the one end portion refers to the end portion of the thread of the bobbin in use and the second end portion of the two end portions refers to the beginning of the thread of the replacement bobbin. Connecting means may be supplemented by or comprise a heat source for supporting the connecting process. A heat source, for example a warm air jet, may for example activate or cure an adhesive or dry a connection .

The apparatus according to the invention may comprise a cutting element for cutting non-connected thread tips off the connected continuous thread. By the cut element, preferably any tip or part of the thread of the connection not being connected, for example not glued together, is cut off. This may be favorable, since loose material might get caught in the apparatus and additional material might get stuck in a thread insertion device. Preferably, a connection between two thread end portions is not performed at the end tips of the thread. This may be done to guarantee that a thread next to a connection fulfills identical specifications as the thread in, for example, the middle of a bobbin, since tips of threads may for example be frayed due to a gripping of the thread tips. If the connection is not performed at the end tips of the threads, such end tips do not form part of the connection and may thus be cut off by the cutting element.

The apparatus according to the invention may comprise a mount for two or more bobbins, for example up to eight bobbins of thread. Preferably, the two or more bobbins are arranged on a revolver system. In the revolver system, one of the bobbins is in an active position and at least one bobbin is in a passive position. In the active position, thread is unwound from the bobbin. In the passive position, the bobbin may be prepared for the splicing, may be loaded onto the revolver system or unloaded from the revolver system.

Preferably, the apparatus according to the invention comprises a tensioning unit that is arranged downstream of the compensation drum. The tensioning unit is configured to maintain the tension of the thread as drawn into the subsequent apparatus, such as, for example, a filter making machine. In the event of an interruption of the downstream demand of thread, for example, due to the regular maintenance of the downstream machine, or due to an unintended rupture of the thread, the tensioning unit detects the drop in tension in the thread. Once a drop in thread tension is detected, the unwinding of the thread from the bobbin is stopped and the tensioning unit raises the tension of the thread back to a predetermined tension, substantially corresponding to the average tension during production conditions.

The tensioning unit allows a quick start-up of the unwinding unit after the interruption of the production has been resolved. Also, the tensioning unit thus reduces the amount of waste created during the interruption of the production .

The method and apparatus according to the invention is preferably used in the manufacture of smoking articles, especially in the manufacture of filters or filter elements for smoking articles. The method may be repeated as often as required, such that the supply of a continuous thread, in particular of paper yarn, is no limiting factor in the production of smoking articles or of filters for smoking articles. According to yet another aspect of the invention there is provided a filter maker comprising an apparatus according to the invention and as described herein.

The invention is further described with regard to an embodiment, which is illustrated by means of the following drawings, wherein

Fig. 1 shows an embodiment of a compensation drum and guide arm in normal use;

Fig. 2 shows the embodiment of Fig. 1 with buffer length of continuous thread wound onto the compensation drum;

Fig. 3 shows a loading station with bobbin and replacement shaft.

In Fig. 1 a rotatable drum 1 and a rotatable guide arm 2 are arranged with their rotational axis 23 coaxial to each other. The guide arm 2 is L-shaped with one branch 24 arranged adjacent to one end of the compensation drum 1 and perpendicular to the rotational axis 23. The other branch 25 of the guide arm 2 is arranged parallel to the rotational axis 23 and at a distance to the outer periphery of the compensation drum 1. The guide arm 2 is rotatable around the periphery of the compensation drum 1. The guide arm 2 is provided with guide 26 and pulleys 20,21,22 to guide a continuous thread 4, in particular paper yarn, from a centrally arranged supply portion (at guide 26) of the guide arm 2 over pulley 20 arranged at the proximal end of the second branch 24 of the guide arm 2. The continuous thread 4 is further guided along the second branch 25 of guide arm 2 over pulley 21 arranged at the distal end of the guide arm 2 and is wound onto the compensation drum 2. The thread 4 from the guide arm 2 is further guided by guide 11, a ring, arranged at the compensation drum 1. The thread may be pushed by a roller (not shown) against the compensation drum 1. After being wound around the compensation drum and having performed about one turn, the continuous thread 4 is guided and led over a further pulley 10 and further guides and mechanical dancers to, for example, a filter making machine (not shown) .

A guide and interruption mechanism 7 is provided between compensation drum 1 and a filter making machine. The interruption mechanism 7 comprises two pulleys 71,72, two guiding rings 73, 74, as well as a mechanical dancer 75. The elements of the mechanism 7 are fixed to a plate 76. The plate 76 is removably attached to the support of the compensation drum 1. The plate 76 may be removed from the support if no interruption mechanism 7 is required or if the interruption mechanism 7 shall be replaced, for example by a simple guide mechanism. The thread 4 leaving compensation drum 1 is guided through and over rings 73,74 and pulleys 71,72 and via dancer 75 to the filter making machine. The dancer 75 is flexibly arranged such that a pulling on the thread is compensated by the flexibility of dancer 75. The interruption mechanism 7 may provide for a constant tightening of the thread. However, provision of the interruption mechanism 7 is also favorable when the flow of thread 4 is stopped or restarted, for example, upon interruption of a filter making machine. Preferably, the thread 4 is held in the interruption mechanism 7 such that use may continue as soon as machine arranged downstream of the compensation drum 1 has started. Use of the interruption mechanism 7 is particularly favorable when using paper yarn or other thread that tends to break upon large or irregular pulling forces.

During normal operation, that is, during thread delivery from a bobbin, the guide arm 2 is arranged stationary and the supply speed of continuous thread 4 to the filter making machine is at a given diameter of the compensation drum 1 defined by the rotational speed of the compensation drum 1.

To increase the length of thread 4 on the compensation drum, the compensation drum is further rotated continuously to unwind thread 4. At the same time, the guide arm 2 is rotated around the compensation drum 1 in an opposite direction than the rotational direction of the rotatable drum 1 by a drive (not shown) . By this, additional windings of thread are placed on the compensation drum 1, corresponding to a buffer length 40 of continuous thread as shown in Fig. 2. The buffer length 40 is for example defined by selecting the rotational speed of the guide arm 2 and the time the guide arm 2 is rotated around the compensation drum 1.

For unwinding the buffer length 40 of continuous thread, the drive stops to rotate the guide arm 2 in an opposite direction. The drive either makes the guide arm 2 to rotate with the compensation drum 1 or the guide arm 2 is coupled to the compensation drum, for example by an appropriate latch mechanism, such as for the guide arm to rotate with the compensation drum.

The guide arm 2 is provided with a moving device 5, here a mounting 50 movable on guiding rails 51 (Fig.l) . By the moving device 5, the axial position of the guide arm 2 is displaceable relative to the compensation drum 1. By linearly displacing the guide arm along the rotational axis 23, also the position where the continuous thread 4 is wound onto to compensation drum 1 is varied and linearly displaced. In Fig. 2 the axial distance 27 between compensation drum 1 and guide arm 2 has been extended by a displacement distance corresponding to the width of the band of thread windings formed by the buffer length 40 of continuous thread on the compensation drum. Preferably, the guide arm is displaced such that the individual windings of the continuous thread 4 of the buffer length 40 of continuous thread are arranged next to each other and do not overlie. A displacement may for example be achieved by a worm gear mechanism, such that for example a rotation of the guide arm 2 corresponds to a displacement distance of the continuous thread 4 between about 1.5 mm and about 4 mm for thread diameters, in particular paper yarn diameters, in a range between about 0.7 mm and 1.6 mm. After the continuous thread has been unwound from the compensation drum 1, the guide arm 2 may be moved back via moving device 5 into its initial position and kept stationary again for normal operation of the apparatus as shown in Fig . 1.

In Fig. 3 a loading zone with a bobbin 41 on a shaft 3 and an unloaded replacement shaft 30 is shown. The shaft 3 is mounted via a mount (not shown) on guiding rails 32 for a lateral displacement on these guiding rails 32. Replacement shaft 30 is arranged parallel to shaft 3 and is provided for holding a replacement bobbin (not shown) . Also the replacement shaft 30 is mounted via a mount on guiding rails 32 for a lateral displacement of the replacement shaft 30 on these guiding rails 32. Shaft 3 and replacement shaft 30 are displaceable such that the rotational axis of the two shafts are aligned with each other for connecting the continuous thread from bobbin 41 to the continuous thread of a bobbin on the replacement shaft. When the thread on the bobbin 41 which is the bobbin in actual use has come to an end, shaft 3 stops to rotate and an end portion of the thread from bobbin 41 in use is preferably held in the center portion of the shaft 3. The beginning of the thread from the replacement bobbin is preferably fixed in a center portion of the replacement shaft 30. Two compression arms 60 arranged to be moved against each other and perpendicular to the orientation of the shaft 3, compress the two ends of thread. An applicator 61 is provided next to one of the compression arms 60 to apply glue or another adhesive to the end portions of the thread. A warm air jet may be provided by an air provider 62 and support the connecting of the threads, for example by activating the glue. A scissor (not shown) may also be provided to cut loose thread ends after having connected the two threads . When the connection is completed the replacement shaft 30 starts rotating and the thread is again provided to the compensation drum 1 (now from the replacement bobbin) and from there to the filter making apparatus. The buffer length 40 of continuous thread 4 that had been wound onto the compensation drum 1 before has been unwound during connecting the threads and replacement of bobbins. Thereby, the unwinding has bridged the time period the connecting needed. The operation as has been described is repeated in order to guarantee a continuous flow of thread to be supplied to the filter making machine .

By way of example only and not meant as limiting, an operational speed of a filter making machine is about 10 m/s. An average amount of continuous thread on a bobbin lasts for about 15 min to supply thread to the compensation drum, with a thread diameter of for example 0.8 mm. With a thread diameter of for example 1.4 mm, the duration is limited to about 7 minutes. The time a connecting of threads of two bobbins requires is about 30 seconds to 1 minute such that a buffer length 40 of thread is preferably predetermined to bridge a time period of about 1 minute. With the apparatus and method according to the invention a continuous supply of thread at about 10 m/s operational speed may be achieved.