This application claims priority on Finnish Application No. 20045069, Filed Mar. 11, 2004, the disclosure of which is incorporated by reference herein.
Not applicable.
The invention relates to a vacuum belt conveyor for transferring a web threading tail in a web manufacturing machine, the belt conveyor comprising
WO publication No. 03018909 discloses a vacuum belt conveyor according to the preamble, which is characterized by a vacuum effect in connection with the first roll. Thus the vacuum can be used to detach the web threading tail from a dryer surface, for example, without separate air blows or doctors. In the proposed tail threading device the vacuum is generated for the first roll with a venturi, which has a ring nozzle. The ring nozzle is located outside the vacuum belt conveyor, at the end of its pipe bracket. From the pipe bracket the vacuum is distributed by means of a bent pipe to a vacuum chamber arranged inside the frame construction and further to the first roll.
Locating the venturi at the end of the pipe bracket complicates the construction of the vacuum belt conveyor, which increases the purchase costs of the apparatus. In addition, the operating efficiency of the venturi is poor. The situation is further impaired by the distance of the venturi from the roll. In practice, a significant part of the vacuum discharges in the constructions, which further impairs the total operating efficiency of the venturi and increases the operating costs of the vacuum belt conveyor. Vacuum adjustment is also difficult and a great amount of compressed air is required for achieving a sufficient vacuum.
The object of the invention is to provide a new type of vacuum belt conveyor, for transferring a web threading tail in a web manufacturing machine, which has a simpler construction than heretofore and with which it is possible to create a vacuum effect more advantageously than heretofore. In the vacuum belt conveyor according to the invention, the vacuum means required for the underpressurization of the first roll are arranged in the frame construction. Thus the vacuum is not created until at the application point, avoiding thus losses caused by flow resistances, for example. The operating efficiency of the vacuum means is also otherwise better than is known in the art and the vacuum level can be adjusted if required. The vacuum means can also be used as part of the frame construction, which further simplifies the construction of the vacuum belt conveyor. At the same time, projecting parts are avoided, which would collect loose material on top.
The invention is described below in detail by making reference to the enclosed drawings illustrating some of the embodiments of the invention.
A vacuum belt conveyor 9 according to the invention is used particularly for transferring and guiding a web threading tail in paper and board machines and other similar web manufacturing machines. The vacuum belt conveyor 9 is later referred to simply as a conveyor.
In the conveyor 9 illustrated in
As shown in
The conveyor 9 also comprises a first vacuum means 22 for creating a vacuum effect in the part of the belt loop 20 that transports the web threading tail 14. Further, the conveyor 9 comprises second vacuum means 23 for creating a vacuum effect in connection with the first roll 16 of the two rolls. Consequently, the web threading tail 14 can be detached from the dryer 11 surface as shown in
The detachment of the web threading tail can be ensured with air doctors 24, which are arranged in connection with the second roll 17, as shown in
According to the invention, the second vacuum means 23 are arranged in the frame construction 15. In this case the vacuum to be introduced to the first roll 16 is created inside the belt loop 20. This simplifies the conveyor construction and improves the operating efficiency of the vacuum means. In the embodiments set forth the second vacuum means 23 are composed of an air blowing apparatus 25. In practice, the air blowing apparatus 25 is composed of a functional blow plate 26 and an air distribution pipe 27 connected thereto. Thus the vacuum is generated near the application point and it is evenly distributed to the first roll 16. According to
The requirement for the operation of a conveyor as described above is a vacuum effect arranged in connection with the first roll. In the embodiment of
Preferably arranged inside the belt loop 20 there is a vacuum chamber 30, in which a vacuum is arranged using the second vacuum means 23 according to the invention. From the vacuum chamber 30 the vacuum extends to the belt loop via the roll grooves, which allows generating the force that is required for detaching the web threading tail. Here the vacuum chamber 30 is delimited by the air distribution pipe 27 and the blow plate 26 arranged in connection with it. Together with the blow plate 26, the air blow discharging from the air distribution pipe 27 creates a so-called coanda effect. In practice the air blow conveys surrounding air with it. The thus created air deficiency generates a vacuum that extends to the web threading tail through the belt loop. For example in the embodiment of
In the embodiment of
In practice, the air distribution pipe 27 thus comprises nozzle holes 35 arranged at a distance from each other in the cross direction of the frame construction for providing air blowing. The size and relative positioning of the nozzle holes can be used to influence the intensity of the vacuum created. On the other hand, the vacuum effect can also be adjusted by changing the air volume used and its overpressure. If required, the nozzle holes are composed of adjustable nozzles. In addition, the air blowing apparatus is oriented in the longitudinal direction of the belt loop. In other words, the air blows are in the longitudinal direction of the conveyor, thus avoiding disturbing side flows.
In the embodiment of
In the embodiments of
In addition to the above, it is also possible to use one or more vacuum boxes 38, as in the conveyor 42, shown in
A vacuum belt conveyor according to the invention is simpler than heretofore and thus more economical to manufacture. By combining constructions and functions it is possible to avoid for example piping, which brings further savings. Practical tests have additionally shown that the required vacuum is achieved with a compressed air amount of as much as 40 percent smaller than heretofore. In addition, the vacuum can be adjusted more easily and accurately than before.
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Number | Date | Country | |
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20050230447 A1 | Oct 2005 | US |