P/00/0 I I Regulation 3.2 AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION Invention Title: Method and structure for separation of web material in winding machine The following statement is a full description of this invention, including the best method of performing it known to me: EDITORIAL NOTE APPLICATION NUMBER - 2010202762 The following page is also numbered 1 METHOD AND STRUCTURE FOR SEPARATION OF WEB MATERIAL IN WINDING MACHINE FIELD OF THE INVENTION The present invention relates to tearing and thus separation of web material, and in particular to a method and a structure for separation of web material in a winding machine. BACKGROUND OF THE INVENTION A conventional winding machine comprises an upper winding roller, a guide plate, a lower winding roller, and a rider roller. The guide plate is arranged at a location close to and below a circumferential surface of the upper winding roller and forms a channel with the upper winding roller. The upper winding roller, the lower winding roller, and the rider roller form therebetween a winding nip. A core around which a web material is wound to form a roll of paper is fed by a conveyor to a location beside the upper winding roller and is then pushed by a core inserter into a passage delimited by the guide plate to reach the winding nip where the web material is wound around the core to form the roll of paper, such as a roll of toilet tissue. After completion of the winding operation of a roll of paper, a rotatable arm is controlled to have a speed that is faster or slower than the rotational speed of the upper winding roller in order to induce a speed difference by which the web material is torn and thus separated. Another known technique uses a method and a structure that realizes separation of web material with physical engagement. For example, a driving arm is positioned against a surface of an upper winding roller arranged in a winding machine to hold down a web material passing through the surface of the upper winding roller. The web material is then torn and thus separated by a pulling force induced by a roll of paper that is formed in a winding nip by wounding the paper around a core.
SUMMARY OF THE INVENTION However, in the above discussed conventional winding machine, care must be taken for the rotatable arm to rotate at a speed not equal to that of an upper winding roller in order to pull apart the web material through a difference in speed. In case the web material is made of a tough material, the speed difference between the rotatable arm and the upper winding roller must be sufficiently large, otherwise the web material would not be pulled apart by the speed difference. In the known web material separation technique that employs physical engagement, the driving arm must be positioned to physically contact the surface of the upper winding roller. This causes certain concerns about the durability and operation safety of the components and parts of the machine. Thus, an objective of the present invention is to provide a winding machine comprising a separation mechanism that tears up and separates a web material with a non-physical-engagement type operation. Another objective of the present invention is to provide a winding machine that comprises an evacuation device and a separation mechanism comprising a suction channel and a passage. A further objective of the present invention is to provide a method and a device for separation of web material in a winding machine that employ a vacuum suction force to separate the web material. The solution adopted in the present invention to overcome the problems of the conventional techniques comprises a winding machine that comprises an upper winding roller and a separation mechanism arranged at a location close to and below a circumferential surface of the upper winding roller. The separation mechanism comprises a pivot shaft having an outer circumferential surface and at least one pinch arm having a connecting end and a web engagement end. The connecting end is coupled to the outer circumferential surface of the 2 pivot shaft. The web engagement end extends outward from the outer circumferential surface of the pivot shaft. When the pinch arm is driven by a driving mechanism to rotate the web engagement end of the pinch arm to an engagement position where the web engagement end opposes the upper winding roller, the web engagement end of the pinch arm sucks and holds or guides a web material passing therethrough, whereby the web material is subjected to a pulling force induced by a roll of paper formed in a winding nip to tear and thus separate. With the solution provided by the present invention, the pinch arm is allowed to tear a web material fed through a winding machine without physical contact with an upper winding roller of the machine. Thus, smoothness and safety of the operation of the winding machine are enhanced and mechanical durability of the components and parts of the winding machine is improved. Accordingly, in a first aspect, the invention provides a method for separating web material in a winding machine, which comprises an upper winding roller, at least one guide plate, a lower winding roller, and a rider roller, wherein the guide plate is arranged at a location close to and below the upper winding roller and forms a channel with the upper winding roller, the upper winding roller, the lower winding roller, and the rider roller forming therebetween a winding nip, a separation mechanism being arranged below the upper winding roller and comprising a pivot shaft and a pinch arm extending from the pivot shaft, the pinch arm having a web engagement end that forms at least one suction opening, the method comprising the following steps: (a) having a web material borne on a lower circumferential surface of the upper winding roller that is rotatable in a predetermined rotation direction to have the web material fed into and passed through the channel; (b) winding the web material which passes through the channel around a first core in the winding nip to form a paper roll; (c) rotating the pinch arm to have the web engagement end periodically reaching an engagement position where the web engagement end opposes the upper winding roller, 3 the web engagement end of the pinch arm being engageable with the web material at the engagement position and maintaining a predetermined spacing from the upper winding roller; (d) causing the suction opening to sucks and holds the web material that passes through the channel at the time when the web engagement end of the pinch arm is at the engagement position; and (e) subjecting the web material to a pulling force induced by the paper roll that is formed in the winding nip so as to tear and thus separate the web material at a location that is between the engagement position and the paper roll of the first core Preferably, the pinch arm is rotatable in a direction opposite to the predetermined rotation direction of the upper winding roller. Preferably, in step (a), before the web material is fed into the channel, the web material is subjected to perforation to form lines of perforations at a fixed interval. Preferably, step (c) further comprises a sub-step of reducing rotational speed of the lower winding roller to have the web material slightly slackened In a second aspect, the invention provides a method for separating web material in a winding machine, which comprises an upper winding roller, at least one guide plate, a lower winding roller, and a rider roller, wherein the guide plate is arranged at a location close to and below the upper winding roller and forms a channel with the upper winding roller, the upper winding roller, the lower winding roller, and the rider roller forming therebetween a winding nip, a separation mechanism being arranged below the upper winding roller and comprising a pivot shaft and a pinch arm extending from the pivot shaft, the pinch arm having a web engagement end, the method comprising the following steps: (a) having a web material borne on a lower circumferential surface of the upper winding roller that is rotatable in a predetermined rotation direction to have the web material fed into and passed through the channel; 4 (b) winding the web material which passes through the channel around a first core in the winding nip to form a paper roll; (c) rotating the pinch arm to have the web engagement end periodically reaching an engagement position where the web engagement end opposes the upper winding roller, the web engagement end of the pinch arm being engageable with the web material at the engagement position and maintaining a predetermined spacing from the upper winding roller; (d) feeding a second core into the channel; (e) reducing rotational speed of the lower winding roller to have the web material slightly slackened within the channel to form a slack portion; (f) guiding the slack portion of the web material with the web engagement end of the pinch arm to have at least a portion of the slack portion of the web material clamped between the second core and the guide plate; and (g) subjecting the web material to a pulling force induced by the paper roll that is formed in the winding nip so as to tear and thus separate the web material at a location that is between the location where the web material is clamped between the second core and the guide plate and the paper roll of the first core. Preferably, the pinch arm is rotatable in a direction opposite to the predetermined rotation direction of the upper winding roller. Preferably, in step (a), before the web material is fed into the channel, the web material is subjected to perforation to form lines of perforations at a fixed interval. Preferably, the method further comprises a step of forming a vacuum suction force at the web engagement end of the pinch arm to assist the web engagement end of the pinch arm to guide and clamp the at least one portion of the slack portion of the web material between 5 the second core and the guide plate. In a third aspect, the invention provides a structure for separating web material in a winding machine, which comprises an upper winding roller, at least one guide plate, a lower winding roller, and a rider roller, wherein the guide plate is arranged at a location close to and below the upper winding roller and forms a channel with the upper winding roller, the upper winding roller, the lower winding roller, and the rider roller forming therebetween a winding nip, a web material being fed into and passing through the channel to form a paper roll in the winding nip by being wound around a first core, a separation mechanism being arranged at a location close to and below the upper winding roller, the separation mechanism comprising: a pivot shaft, which has an outer circumferential surface; at least one pinch arm, which is coupled to the outer circumferential surface of the pivot shaft, the pinch arm having a connecting end and a web engagement end, the connecting end being fixedly mounted to the outer circumferential surface of the pivot shaft, the web engagement end extending outward from the outer circumferential surface of the pivot shaft and forming at least one suction opening; a driving mechanism, which is connected to the pivot shaft to drive the pinch arm to rotate about the pivot shaft so as to have the web engagement end of the pinch arm periodically set on an engagement position or off the engagement position, the web engagement end of the pinch arm being engageable with the web material at the engagement position and maintaining a predetermined spacing from the upper winding roller; a suction channel, which is formed inside the pivot shaft and communicates the suction opening of the web engagement end through a passage; and an evacuation device, which is connected to the pivot shaft and communicates with the suction channel to form a vacuum suction force at the suction opening of the web engagement end of the pinch ann; 6 wherein when the pinch arm is driven by the driving mechanism to have the web engagement end of the pinch arm reaching the engagement position, the suction opening of the web engagement end of the pinch arm sucks and holds the web material passing through the channel whereby the web material is subjected to a pulling force induced by the paper roll formed in the winding nip to tear and thus separate at a location between the engagement position and the paper roll of the first core. Preferably, the pinch arm is rotatable in a direction opposite to the predetermined rotation direction of the upper winding roller. Preferably, the structure further comprises a perforation device, which is arranged at a location close to the channel in order to form lines of perforations at a fixed interval in the web material before the web material is fed into the channel. In a fourth aspect, the invention provides a structure for separating web material in a winding machine, which comprises an upper winding roller, at least one guide plate, a lower winding roller, and a rider roller, wherein the guide plate is arranged at a location close to and below the upper winding roller and forms a channel with the upper winding roller, the upper winding roller, the lower winding roller, and the rider roller forming therebetween a winding nip, a web material being fed into and passing through the channel to form a paper roll in the winding nip by being wound around a first core, a separation mechanism being arranged at a location close to and below the upper winding roller, the separation mechanism comprising: a pivot shaft, which has an outer circumferential surface; at least one pinch arm, which is coupled to the outer circumferential surface of the pivot shaft, the pinch arm having a connecting end and a web engagement end, the connecting end being fixedly mounted to the outer circumferential surface of the pivot shaft, the web engagement end extending outward from the outer circumferential surface of the pivot shaft; 7 a driving mechanism, which is connected to the pivot shaft to drive the pinch arm to rotate about the pivot shaft so as to have the web engagement end of the pinch arm periodically set on an engagement position or off the engagement position, the web engagement end of the pinch arm being engageable with the web material at the engagement position and maintaining a predetermined spacing from the upper winding roller; wherein when the pinch arm is driven by the driving mechanism to have the web engagement end of the pinch arm reaching the engagement position, the web engagement end of the pinch arm guides at least one portion of a slack portion of the web material within the channel to have the at least one portion clamped between a second core and the guide plate, whereby the web material is subjected to a pulling force induced by the paper roll formed in the winding nip to tear and thus separate at a location between the location where the at least one portion clamped between the second core and the guide plate and the paper roll of the first core. Preferably, the pinch arm is rotatable in a direction opposite to the predetermined rotation direction of the upper winding roller. Preferably, the structure further comprises a perforation device, which is arranged at a location close to the channel in order to form lines of perforations at a fixed interval in the web material before the web material is fed into the channel. BRIEF DESCRIPTION OF THE DRAWINGS The present invention will be apparent to those skilled in the art by reading the following description of preferred embodiments of the present invention and the best modes for carrying out the present invention, with reference to the attached drawings, in which: Figure 1 is a schematic side elevational view showing a winding machine in accordance with a first embodiment of the present invention; Figure 2 is a schematic view showing formation of lines of perforations in a web material at 8 a fixed interval according to the present invention; Figure 3 is a schematic side view showing an upper winding roller and a pinch arm of a separation mechanism of the winding machine in accordance with the present invention; Figure 4 is a cross-sectional view showing the separation mechanism according to the present invention; Figure 5 is a schematic side view showing a first view of separation of web material by the winding machine according to the first embodiment of the present invention; Figure 6 is a schematic side view showing a second view of separation of web material by the winding machine according to the first embodiment of the present invention; Figure 7 is a schematic side view showing a third view of separation of web material by the winding machine according to the first embodiment of the present invention; Figure 8 is a schematic side view showing a fourth view of separation of web material by the winding machine according to the first embodiment of the present invention; Figure 9 is a schematic side view showing a fifth view of separation of web material by the winding machine according to the first embodiment of the present invention; Figure 10 is a schematic side view showing a sixth view of separation of web material by the winding machine according to the first embodiment of the present invention; Figure 11 is a schematic side view showing a seventh view of separation of web material by the winding machine according to the first embodiment of the present invention; Figure 12 is a schematic side view showing an eighth view of separation of web material by the winding machine according to the first embodiment of the present invention; Figure 13 is a schematic side view showing a first view of separation of web material by the 9 winding machine according to a second embodiment of the present invention; Figure 14 is a schematic side view showing a second view of separation of web material by the winding machine according to the second embodiment of the present invention; Figure 15 is a schematic side view showing a third view of separation of web material by the winding machine according to the second embodiment of the present invention; Figure 16 is a schematic side view showing a fourth view of separation of web material by the winding machine according to the second embodiment of the present invention; Figure 17 is a schematic side view showing a fifth view of separation of web material by the winding machine according to the second embodiment of the present invention; Figure 18 is a schematic side view showing a sixth view of separation of web material by the winding machine according to the second embodiment of the present invention; Figure 19 is a schematic side view showing a seventh view of separation of web material by the winding machine according to the second embodiment of the present invention; and Figure 20 is a schematic side view showing an eighth view of separation of web material by the winding machine according to the second embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS With reference to the drawings and in particular to Figure 1, a winding machine constructed in accordance with a first embodiment of the present invention, broadly designated at 100, comprises a machine frame 11, an upper winding roller 12, a plurality of guide plates 13 (only one being visible in a schematic side elevational view shown in Figure 1), a separation mechanism 14, a lower winding roller 15, a rider roller 16, a core conveyor 17, a pair of feed rollers 21, a perforation device 22, an inclined chute 23. The guide plates 13 are located at positions near and below the upper winding roller 12 such 10 that a channel 3 is formed between the guide plates 13 and the upper winding roller 12. A winding nip 19 is formed between the upper winding roller 12, the lower winding roller 15, and the rider roller 16. A long tape of web material 4 that has a predetermined thickness and width is fed along a feeding direction Il by the feed rollers 21 to pass through the perforation device 22 that forms a line of perforations 41 that extends in a direction substantially normal to the feeding direction 11 at a fixed interval (see Figure 2). The web material tape is then moved to bear against a lower circumferential surface of the upper winding roller 12 and wound around a first core 5 at the winding nip 19 to thereby form a roll of paper 51 having a predetermined diameter, such as a roll of toilet paper. Referring to Figure 3, the separation device 14 is arranged near and below the upper winding roller 12. The separation device 14 comprises a pivot shaft 141 and at least one pinch arm 142. The pivot shaft 14 comprises an outer circumferential surface 141a and the pinch arm 142 is coupled to the outer circumferential surface 141a of the pivot shaft 141. Each pinch arm 142 has a connecting end 142a and a web engagement end 142b. The connecting end 142a is fixedly mounted to the outer circumferential surface 141a of the pivot shaft 141, and the web engagement end 142b extends outward from the outer circumferential surface 141a of the pivot shaft 141. A driving mechanism (not shown) drives the pinch arm 142 to rotate about the pivot shaft 141. The pinch arm 142 is rotatable in a rotation direction 13 that is opposite to a rotation direction 12 of the upper winding roller 12 so that the web engagement end 142b of the pinch arm 142 is rotated to be selectively set on an engagement position A or off the engagement position A. The rotation of the pinch arm 142 defines a circular rotation locus 142d. Also referring to Figure 4, the web engagement end 142b of the pinch arm 142 forms a suction opening 142c. The pivot shaft 141 is a hollow tube forming internally a suction channel 141b. The pivot shaft 141 forms a plurality of apertures 141c in the outer circumferential surface 141a at predetermined positions to communicate the suction channel 141b. The pinch arm 142 forms internally at least one passage 142e communicating the suction opening 142c and the aperture 141c of the pivot shaft 141. An evacuation device (not shown) is connected to the pivot shaft 141 to remove air from the suction channel 141b 11 of the pivot shaft 141 and the passage 142e of the pinch arm 142, so that the web engagement end 142b of the pinch arm 142 may establish a vacuum suction force at the suction opening 142c. Preferably, the suction opening 142c of the web engagement end 142b shows a recessed structure so that an excellent suction effect can be realized by the suction opening 142c to attract and hold the web material 4. Referring to Figures 5-12, a sequence of operations are performed by the winding machine according to the first embodiment of the present invention to tear and thus separate the web material. When the pinch arm 142 is driven to rotate along the rotation direction 13, the web engagement end 142b of the pinch arm 142 is periodically rotated to reach the engagement position A where the web engagement end 142b of the pinch arm 142 opposes the upper winding roller 12 (as shown in Figure 6). At this moment, the web engagement end 142b of the pinch arm 142 is put into engagement with the web material 4, but maintains a predetermined spacing from the upper winding roller 12 and is thus not in physical engagement with the upper winding roller 12. The web engagement end 142b of the pinch arm 142 sucks and holds the web material 4 on the suction opening 142c of the pinch arm 142. A second core 6 is carried forward by one of a number of carriers 171 of the core conveyor 17 to a loading nip of the channel 3 formed between the guide plates 13 and the upper winding roller 12. Afterwards, a core inserter 172 of the core conveyor 17 is automatically turned to push the second core 6 into the channel 3 (as shown in Figure 7). In a preferred embodiment of the present invention, to allow the web engagement end 142b of the pinch arm 142 to properly attract and hold the web material 4 passing through the channel 3, the rotational speed of the lower winding roller 15 is controlled by a controller (not shown) to reduce and get slightly slowed down at the time when the web engagement end 142b of the pinch arm 142 reaches the engagement position A, whereby the web material 4 gets partially slackened and hangs down (as shown in Figure 7) to allow the web engagement end 142b of the pinch arm 142 to properly attract and hold the web material 4. When the web material 4 is sucked and held by the web engagement end 142b of the pinch arm 142, the paper roll 51 that is formed by being rolled up in the winding nip 19 applies a 12 pulling force to a right-hand side portion of the web material 4 so as to tear the web material 4, whereby the web material 4 that is so torn forms, at the location where the tearing occurs, a trailing edge 43 in connection with the first core 5 and a leading edge 44 in connection with the second core 6. The trailing edge 43 of the web material 4 keeps moving to and is then wound around the first core 5 to complete the winding operation of the paper roll 51 (see Figure 10). At this point, the lower winding roller 15 resumes the original rotational speed. The location where the web material 4 is torn is between the engagement position A and the paper roll 51 of the first core 5. In a practical application, the location where the web material 4 tears is at the portion of the web material 4 where the perforations 41 are formed by the perforation device 22. When the web material 4 is torn, the web engagement end 142b of the pinch arm 142 sucks and holds the leading edge 44 of the web material 4 and the pinch arm 142 is caused to rotate in an opposite direction to bring the leading edge 44 of the web material 4 to the second core 6 that is just fed into the channel 3, to allow the leading edge 44 of the web material 4 to be primarily wound around an outer circumferential surface of the second core 6. When the pinch arm 142 is rotated to such an extent to get away from the web material 4 and the channel 3, the second core 6 keeps rolling forward along the channel 3, and the leading edge 44 of the web material 4 is completely wound around the second core 6. Meanwhile, the trailing edge 43 of the web material 4 is attached to the paper roll 51 to complete the winding operation of the roll paper 51 (as shown in Figures 10 and 11). Referring to Figures 11 and 12, the second core 6 is transferred to the winding nip 19 due to an effect of speed difference between the upper winding roller 12 and the lower winding roller 15 caused by speed reduction of the lower winding roller 15 (see Figure 12) and the winding operation of a new roll of paper starts. Meanwhile, the completed paper roll 51 is discharged by moving along the inclined chute 23. When the paper roll 51 is being discharged, the rider roller 16 that is connected to a oscillable gripping arm 161 (see Figure 1) having a pivot shaft 162 about which the oscillable gripping arm 161 reciprocally rotates is allowed to do reciprocal rotation about 13 the pivot shaft 162, whereby the rider roller 16 that is connected to the oscillable gripping arm 161 is moved upward and downward, following the reciprocation path of the oscillable gripping arm 161. Thus, when the paper roll 51 has been discharged, the rider roller 16 that initially presses against the paper roll 51 moves downward to press against the second core 6. Referring to Figures 13-20, a sequence of operations of a winding machine in accordance with a second embodiment of the present invention are illustrated. Figures 13-15 illustrate the same operations as those shown in the first embodiment, but in Figure 16, in the normal winding operation of the web material, the rotational speed of the lower winding roller 15 is slightly reduced and thus slowed down to have the web material 4 slackened inside the channel 3 and thus forming a slack portion 42. The slack portion 42 is guided by the web engagement end 142b of the pinch arm 142 (see Figure 17) to have at least a portion thereof (that is adjacent to the second core 6) clamped between the second core 6 and the guide plates 13 (see Figure 18). At this point, the lower winding roller 15 resumes the original rotational speed and a pulling force is applied from the paper roll 51 formed in the winding nip 19 to the web material 4 to tear the web material 4 (see Figure 19). The location where the tearing of the web material 4 occurs is between the location where the web material 4 is clamped between the second core 6 and the guide plates 13 and the paper roll 51 of the first core 5. Similar to the previous embodiment, when the pinch arm 142 is driven to rotate in the rotation direction 13 to bring the web engagement end 142b of the pinch arm 142 to periodically reach the engagement position A where the web engagement end 142b opposes the upper winding roller 12, the suction opening 142c of the web engagement end 142b of the pinch arm 142 generates a suction force, which helps the web engagement end 142b of the pinch arm 142 to clamp at least a portion of the slack portion 42 of the web material 4 between the second core 6 and the guide plates 13. When the web material 4 is torn, the subsequent operations (as shown in Figure 20) are identical to those of the previous embodiment. Although the present invention has been described with reference to the preferred 14 embodiments thereof and the best modes for carrying out the present invention, it is apparent to those skilled in the art that a variety of modifications and changes may be made without departing from the scope of the present invention which is intended to be defined by the appended claims. 15