Field of the invention

The present invention concerns a method and apparatus for transferring a pulp-based web from a first processing apparatus to a second processing apparatus. More specifically, the invention concerns a method for controllably transferring a leader slit from the web from a first processing apparatus to a second processing apparatus.

State of the Art

As a pulp web is formed, it is processed in several different stages at several different apparatuses. Typically, water is squeezed out of a web formed from pulp mass in one appa- ratus after which the web is transferred to another apparatus where it is dried further with e.g. hot air.

Each time this process is started from beginning, for example after maintenance work or a disruption occurred in the process, the web has to be led from a press section to a drying section and further through the whole drying section.

Conventionally this has been done by slitting a narrow strip from the web in its running direction, for example by using a water jet. This strip is led to run in the vicinity of a threading belt, where it is cut. The cut end of the strip, i.e. the leader, coming from the press section is fed to the threading belt, which runs through the drying section alongside with the track on which the web runs. The feeding of the cut end occurs often in connection with the cutting by giving an impulse to the cut end either with the blades used for cutting or with compressed air, for example. The threading belt is often equipped with one or more press wheels or belts, which form a nip with the threading belt at the location where the end of the leader is brought to the threading belt.

After the leader is placed on the threading belt, it is conventionally folded after the press wheel or belt, so that the leader is left inside the folded threading belt. This arrangement ensures that the leader stays with the threading belt throughout the whole drying section. When the leader has run for a sufficiently long distance within the drying section, the leader is gradually widened by moving the point where the leader is slit in a direction transversal to the web until the leader becomes as wide as the whole web. Transferring the cut end of the leader has traditionally been done by hand. Transferring the leader to the threading belt manually is slow and is associated with safety hazards as the apparatus' operator has to work in the vicinity of moving machine parts.

Different apparatuses have thus been developed for transferring a leader to a threading belt. For example, one of these apparatuses has been disclosed in publication WO 2007/108738. A problem with these apparatuses has been to provide a reliable and controlled transfer to the threading belt. It has been particularly problematic to control the running of the leader as it is cut, and immediately after it, while bringing the cut end of the leader into the nip between the threading belt and the press wheel or belt.

Publication WO 99/27184 also discloses an apparatus for transferring a leader from a first processing apparatus to a second processing apparatus. Publication WO 99/39049, in turn, discloses an apparatus wherein a leader is transferred onto a threading belt by using gripping equipment. However, the afore-mentioned problems are not solved by the teachings of these publications.

Summary of the Invention

The purpose of the present invention is to provide a solution to the problems related to transferring a leader to the threading belt, and to provide an improved method and apparatus for performing it. In a solution according to the invention this is realized by brining the leader to run under compression between a transfer wheel and a press wheel at least during the time when the leader is cut and its cut end is brought into compression between the threading belt and the press wheel.

As the leader is under compression during cutting, stable and controlled running of the leader is ensured regardless of the cutting and the subsequent impulses for guiding the cut end to the threading belt. Brief Description of the Drawing

In the following embodiments of the invention are discussed in more detail with reference to the enclosed drawing, wherein;

Figure 1 illustrates a perspective view of an apparatus according to an embodiment of the invention in different stages of its operation;

Figure 2 illustrates a perspective view of an apparatus according to another embodiment the invention in different stages of its operation;

Figure 3 illustrates a perspective view illustrates the embodiment of figure 2 in a stage of its operation from a different angle of view

In figure 1 an apparatus according to an embodiment of the invention is in a state, where a leader 1 and its cut end coming from a first processing apparatus (not shown) has been placed to run onto a threading belt 7. Additionally, illustrated with broken lines with the reference number 12, the positions of a transfer wheel 2 and a cutting device 3 in the beginning stage of the operation of the apparatus are shown. The leader runs between the transfer wheel 2 and the press wheel 8, and further between the press wheel 8 and a threading belt 7. Using the reference number 3 a cutting device is shown with which the leader is cut against a cutting blade 9. The transfer wheel 2 and the cutting device 3 are attached to a transfer carriage 4 moving along a transfer rail 5. It should be noted that for the purpose of clarity, the transfer rail 5 has been illustrated as being shorter than what it in reality could be. The transfer rail 5 is attached to a suitable support structure (not shown) using a mounting 6. The threading belt7 has been turned to run back towards its incoming direction using a caster configuration 10.

In figure 2 an apparatus according to another embodiment of the invention is illustrated in a state where the leader 1 runs over the transfer wheel 2, and the leader has been moved transversally with respect to its running direction so as to run in line with the threading belt 7. Further, reference numeral 11 indicates the position of the transfer wheel 2 and the cutting device 3, illustrated with broken lines, where they receive the leader as it exits the first processing apparatus and prior to being moved transversally. Reference numeral 13 indi- cates the position of the transfer wheel 2 and the cutting device 3, illustrated with broken lines, when the leader has been brought under compression between the transfer wheel 2 and the press wheel 8. From figure 2 an actuator 2' rotating the transfer wheel, an actuator 3' producing the cutting device's cutting motion, an actuator 4' producing the transfer wheel's 2 and the cutting device's transverse motion, and an actuator 5' producing the movement of the carriage 4, can also be seen. In figure 3, the apparatus according to figure 2 can be seen in a state, where the cut end of the leader has been placed on to the threading belt 7.

Detailed Description of the Invention In an apparatus according to one of the invention's embodiments illustrated in figures 2 and 3, the transfer rail's 5 end facing the first processing apparatus is located so that the leader 1 slit from the web and coming from the first processing apparatus runs between the transfer wheel 2 and the second processing apparatus when the carriage 4 has been driven to the end concerned. The transfer rail's 5 end facing the first processing apparatus is also located so that the transfer wheel 2 is located in line with the leader in the web's width direction at the end concerned. The transfer rail's 5 end facing the second processing apparatus, in turn, is located so that the transfer wheel 2 is pushed against the press wheel 8 when the carriage 4 is driven towards the end in question. Alternatively, the transfer rail's 5 end facing the second processing apparatus can also be located so that the transfer wheel 2 is pushed against another wheel located in the vicinity of the press wheel 8 when the carriage 4 is driven towards the end in question.

The carriage 4 is arranged on the transfer rail 5 movably in the direction of the transfer rail. The position of the carriage 4 on the transfer rail can be controlled by the actuator 5', which can be a hydraulic or pneumatic cylinder, a rodless cylinder, a linear motor, a linear guide equipped with a ball screw mechanism or a belt drive, or another linear actuator generally known in the art. The transfer rail 5, in turn, is attached with the mounting 6 to a frame of either one of the processing apparatuses or to a separate support structure, for example. The transfer rail 5 can alternatively be mounted movably and equipped with actuators for moving the transfer rail.

The transfer wheel 2 is attached rotatably to the carriage 4. For producing a rotation mo- tion, the transfer wheel 2 can be coupled with a motor 2', which can be for example a hydraulic, a pneumatic, or an electric motor providing a suitable rotational speed.

Also the cutting device 3, operating in cooperation with the cutting blade 9 located in the vicinity of the press wheel 8 and the threading belt 7, is arranged onto the carriage 4. The cutting device 3 comprises a moving pusher, by which the leader 1 can be cut against the cutting blade 9. The cutting device's 3 pusher can further move past the cutting blade 9 and feed the cut end of the leader between the threading belt 7 and the press wheel 8. The movement of the pusher is achieved with the actuator 3', which can be a hydraulic or a pneumatic cylinder, a solenoid, or another actuator providing a suitable motion. The cut- ting device 3 advantageously comprises at least one jet with which the cut end of the leader can be fed towards the nip between the threading belt 7 and the press wheel 8 using compressed air immediately after the cutting. Said at least one jet can be arranged at the moving pusher, for example. The transfer wheel 2 is advantageously equipped with flanges at its ends for ensuring that the leader stays on the transfer wheel as it moves with the carriage 4 along the transfer rail 5. In such a case, the distance between the flanges is to be greater than the width of the press wheel 8. In an apparatus according to another embodiment of the invention, the carriage 4 can be equipped with an actuator 4' for moving the transfer wheel 2 and the cutting device 3 in a substantially transverse direction to the length direction of the transfer rail 5, in accordance with the figure 2. The actuator 4 can be a rodless hydraulic or pneumatic cylinder, a linear guide equipped with a ball screw mechanism or a belt drive, or another linear actuator known in the art providing a suitable motion.

It is readily apparent to a person skilled in the art that moving parts and actuators can be equipped with several kinds of sensors for producing e.g. speed and location data for controlling the apparatus. In a method according to the invention, as the processing apparatuses are started up the carriage 4 is firstly driven to the transfer rail's 5 end facing the first processing apparatus according to the position illustrated with the reference numeral 12 in figure 1 and 2.When the web coming from the first processing apparatus has been formed so that it can be transferred to the second processing apparatus, a leader is slit from the web as known in the art. As explained previously, when the carriage 4 is in this position, the transfer wheel 2 is located between the first processing apparatus and the leader 1 coming from it, i.e. the leader is between the transfer wheel 2 and the second processing apparatus. The transfer wheel 2 is also located in line with the leader 1 in the width direction of the web at the end in question.

When the carriage 4 is driven towards the transfer rail's 5 end facing the second processing apparatus, the transfer wheel 2 picks up the leader 1, and transfers it to run closer to the second processing apparatus. The carriage 4 is driven towards the transfer rail's end facing the second processing apparatus until the transfer wheel 2 is pushed against the press wheel 8, leaving the leader 1 in a nip between them, thus settling interferences in the running of the leader. As a result of the aforementioned procedures, the running track of the leader 1 has moved to run in the vicinity of the threading belt 7 and the press wheel 8, according to figures 1 and 2, for example.

As the leader 1 is in contact with the transfer wheel 2, the transfer wheel can advantageously be rotated by means of the actuator 2', thus assisting the leader to run over the transfer wheel. As the transfer wheel 2 is rotated during movement of the carriage 4, the peripheral speed of the transfer wheel can be equal to or greater than the track speed of the leader, for example. As the transfer wheel 2 contacts the press wheel 8, the peripheral speed of the transfer wheel should be substantially equal to the track speed of the leader.

Next, the leader is cut by pushing it against the cutting blade 9 by the cutting device's 3 pusher. The cut end of the leader 1 is pushed further pass the cutting blade towards the point where the press wheel 8 and the threading belt 7 contact each other. Simultaneously, an airflow can be exerted from the cutting device's nozzles to ensure that the cut end is led into the nip between the press wheel 8 and the threading belt 7. The press wheel 8 pushes the cut end of the leader against the threading belt 7, which further conveys the leader throughout the second processing apparatus.

According to another embodiment of the invention, moving of the leader 1 transversally so as to be in line with the threading belt 7 is achieved by moving the transfer wheel 2 and the cutting device 3 with the actuator 4' during the movement of the carriage 4 or prior to it. This can be particularly advantageous if the invention is implemented on an existing processing apparatus, where the transferring apparatus has been installed next to the web track. The above-described transversal movement is realized in figure 2 between the positions having the reference numerals 11 and 12, for example.

It is obvious to the person skilled in the art, that the apparatus and method according to the invention can also be used for transferring a leader from a first processing apparatus to a second processing apparatus being equipped with another kind of conveying means instead of the threading belt 7 for conveying the leader throughout the second processing apparatus.