Suction braking device for feeding at a constant tension a continuous web of paper, or the like

Abstract: This invention relates to a suction/braking device for feeding at a constant tension a continuous web of paper, or the like, comprising a perforated annular section for braking the speed of a web of paper (N) associated with a stationary suction chamber (12), whereby the speed of paper web (N) which is passing over the annular web-braking section (10), is slowed down by the suction being applied thereon through the suction ports (110) in communication with the suction chamber (12). According to the invention, the perforated web-braking annular section forms part of a perforated web-braking cylindrical drum (10) which is mounted so as to be rotatable around its axis over a stationary suction chamber (12) formed in the inside of this drum, means (13, 25) being provided for cleaning the suction ports (110) in the annular section of the peripheral wall of the web-braking cylindrical drum (10), particularly for clearing them from any paper dust having settled in the said suction ports (110), which means are associated with a zone other than the zone in which the suction chamber (12) is formed.

Description: The object of the invention is a suction braking device for feeding at a constant tension a continuous web of paper or the like, provided in a machine for unwinding a paper web from a bobbin between pay-off means and any desired web-using machine, particularly of the type as employed in the tobacco industry, the said device comprising a perforated annular section for braking the speed of a web of paper which is associated with a stationary suction chamber, whereby the speed of the paper web that is passing over the annular web-braking section, is slowed down by the suction being applied thereon through the suction ports in communication with the suction chamber. A suction braking device of this kind is known from the document GB-A-2 171 286. From the document DE-A-3 100 814, the use is known of a perforated cylindrical drum which is mounted so as to be rotatable around its axis over a stationary suction chamber formed in the inside of this drum, for applying a suction through the drum ports in communication with the suction chamber, while for generating an air-blow through the drum ports, in the drum inside a stationary air-blowing chamber is formed in a substantially diametrically opposite position to the suction chamber. This perforated rotatable known drum which is associated with a stationary suction chamber and a stationary air-blowing chamber in the inside thereof, however is not for braking a continuous web of paper so as to feed it at a constant tension to a web-using machine, but is for entraining and driving forward a web. The air-blowing chamber does not serve the purpose of clearing the drum ports, but the purpose of assuring a correct separation of the web from the drum. Also from the document DE-A-2 254 971 the use is known in the tobacco industry of a perforated rotatable drum which is associated with a stationary suction chamber and a stationary air-blowing chamber in the inside thereof. However, also this drum is not for braking a continuous web of paper, but is for transferring cigarettes and paper tabs. The air blown out from the air-blowing chamber through the drum ports serves the purpose of separating and blowing off loose paper tabs, i.e., the tabs whose winding on cigarettes failed to occur. These tabs are collected into a box that however is not a suction box and is not arranged close to the air-blowing chamber. In the known suction braking devices of the type as described at the outset and in the pre-characterizing part of claim 1, some inconveniences are found, that reside in the suction ports in the annular web-braking section becoming gradually clogged. Such a clogging of the suction ports in the annular web-braking section is due to the presence of paper dust on a paper web. Paper dust gradually fills the suction ports in the annular web-braking section as a paper web is being caused to slide thereon. The fact that the suction ports in the annular web-braking section become clogged results in the web-braking effect being decreased, and so in the tension at which a web is fed to the web-using machine being undesirably changed, which brings about a malfunctioning of the web-using machine. This invention aims to provide a suction/braking device of the type as disclosed at the outset, which is such that owing to simple and not much expensive means being used for making the same, any inconveniences in the known web-braking devices are eliminated. The invention attains this object by the combination of the features as set forth in the characterizing part of claim 1. The advantages of the present invention will clearly appear from the foregoing. Thanks to an extremely simple and not much expensive construction, the suction ports in the annular section of the peripheral wall of the web-braking cylindrical drum are continuously cleared from dust, whereby any negative effect on the web braking and on the web feeding tension, are eliminated. Also other features further improving the above disclosed suction/braking device also form the object of the invention, and are the subject of the dependent Claims. The particular features of the invention and the advantages arising therefrom will appear more in detail from the specification of one preferred embodiment thereof, shown by way of a non-limiting example in the accompanying drawings, in which: Figure 1 is a diagrammatic view showing a paper web feeding machine in which a suction/braking device in accordance with the invention, is applied. Figure 2 is an axial sectional view of the web-braking device in accordance with the invention. Figure 3 is a cross-sectional view of the web-braking device according to Figure 2. Referring to Figure 1, there is shown that a suction/braking device 1 for feeding at a constant tension a continuous web of paper to a web-using machine, is located downstream of a paper web buffer magazine 2 and upstream of a web-using machine, not shown. A paper web N is unwound from a bobbin 3, located upstream of the buffer magazine 2. The device 4 for paying off a paper web from the respective bobbin is preferably adapted to simultaneously accomodate a pair of bobbins, that is, a bobbin 3 from which the web N is paid off, and a reserve bobbin 3'. Between the paper web pay-off device 4 and the paper web buffer magazine 2 a splicing means 5 is provided, through which the web N being unwound from bobbin 3 is passed, and in which the leading free end of web N' from the reserve bobbin 3' is received. When a bobbin 3 is about to be depleted, the splicing means 5 is caused to splice the trailing end of web N from the just depleted bobbin 3 with the leading free end of web N' from the reserve bobbin 3'. Thanks to the paper web buffer magazine 2, the splicing of the trailing end of web N with the leading free end of web N' is generally performed with the webs N, N' being kept in their stationary condition. The depleted bobbin 3 is then replaced with a complete bobbin which as the web is being unwound from bobbin 3', becomes in its turn the reserve bobbin. Since web-using machines are operated at a web-processing speed which normally is different from, particularly lower than the speed at which a paper web is being unwound from its bobbin, and since the paper web N tensioning and paying-off speed are subject to vary, the provision of the web-braking device 1 downstream of the paper web buffer magazine 2 renders it possible to have a paper web N fed at a constant tension to a web-using machine, whereby a proper operation of the machine is ensured. The web-using machines may be of any type, and may be, for example, packing machines, or the like. This invention refers particularly to web-using machines applied to the field of the tobacco industry. According to Figures 2 and 3, the web-braking device of the invention is of the suction type, and consists of a perforated web-braking cylindrical drum 10. The suction ports 110 in drum 10 are distributed over the entire annular section of its peripheral wall, preferably in the fashion of a plurality of circularly arranged parallel rows of ports. The web-braking drum 10 is mounted so as to be rotatable around its axis on a drum-supporting cylindrical body 11, and is made substantially air-tight to the ambient atmosphere. The said drum-supporting cylindrical body 11 is stationary, and is formed in a peripheral portion thereof with an arcuate suction chamber 12, with its outward side being closed by the peripheral wall of the said web-braking cylindrical drum 10. Through the suction ports 110 in that portion of the annular section of the cylindrical web-braking drum 10 peripheral wall, which is being respectively associated with the arcuate suction chamber 12, a suction is applied on the web (not shown) that is sliding over the said portion of the annular section of drum 10 peripheral wall, and a braking effect on the web speed is thus produced. The said arcuate suction chamber 12 is preferably formed in the upper region of the cylindrical body 11. The drum-supporting cylindrical body 11 is also formed in its peripheral region which is diametrically opposite to the suction chamber 12, with an air-blowing chamber 13 in direct communication with the perforated annular section of the peripheral wall of drum 10, just as the suction chamber 12 is. The drum-supporting cylindrical body 11 is secured to the one end side of a distributor sleeve 14, with its opposite, other end side being formed with a flange 114. By this flange the said sleeve is secured by means of screws 15 to the device frame 9. A suction duct 16 is formed in the distributor sleeve 14 and opens into the suction chamber 12 in the drum-supporting cylindrical body 11, and through a pipe 17 the said duct is connected to a vacuum generator (not shown). The said distributor sleeve 14 is also formed with an air-blowing duct 18 opening into the air-blowing chamber 13 in the drum-supporting cylindrical body 11. The air-blowing duct 18 is connected through a pipe 19 to a pressure generator, preferably to a compressed air source (not shown). The cylindrical drum 10 has its central area secured to the flange 120 of a shaft 20 for driving this drum in rotation, which is passed through the drum-supporting cylindrical body 11, and is rotatably supported therein by bearings 21. The free end of shaft 20 for driving the drum 10 in rotation, extends into the distributor sleeve 14, where the said shaft free end is connected through a coupling 22 to the shaft 123 of a geared motor 23, which is preferably electrically actuated by a direct current. By means of a flange 24 which is integral with the geared motor 23, the said geared motor is fastened to the flange 114 for fixing the distributor sleeve 14 in position. According to a further feature of the invention, a collection and discharge chamber 25 is provided on the outside of the perforated annular section of the web-braking drum 10 peripheral wall, close to the air-blowing chamber 13. The collection and discharge chamber 25 is open to drum 10 and bears against this drum in a substantially air-tight condition relative to the ambient atmosphere. Through a suction duct 26 and a successive pipe 27 this chamber is connected to a vacuum generator (also not shown). The web of paper (not shown) is caused to slide on that portion of the perforated annular section of the web-braking drum 10 peripheral wall which is being respectively associated with the stationary suction chamber 12. Thus, through the suction ports 110 in the said portion of the perforated annular section of drum 10 periperal wall, a suction is applied on the paper web surface, whereby the web speed is slowed down. Owing to drum 10 being rotated about the drum-supporting cylindrical body 11, the suction ports 110 in said drum will be alternatingly set in communication with the suction chamber 12 and the air-blowing chamber 13. Therefore, any paper dust settling in the suction ports 110, and partly or entirely clogging these ports while this dust is being drawn thereover, is blown out of the suction ports 110, into the collection and discharge chamber 25, at the time the said suction ports come to be set in communication with the air-blowing chamber 13. The paper dust blown into the collection and discharge chamber 25 is then sucked away therefrom. Hence, the suction ports 110 in drum 10 are always perfectly clear throughout their width at the time these ports come to be set in communication with the suction chamber 12, so that a perfect braking of the web speed is ensured. This allows any undesired change in the paper web feeding tension to be prevented, which would generally bring about a malfunctioning of the successive web-using machine. According to a further improvement of the invention, the web-braking drum 10 is provided on either sides of the perforated annular section of its peripheral wall with a web-guiding annular rim 210 which protrudes radially from the surface of the annular section of said drum peripheral wall. This pair of oppositely arranged web-guiding rims 210 advantageously prevent that a paper web may be excessively displaced sideward, thus guaranteeing that the web surface will always cooperate with all of the suction ports 110 in the respective portion of the perforated annular section of drum 10 peripheral wall, on which the said web is sliding, and which is associated with the suction chamber 12. This renders it possible to avoid any undesired change in the web braking, resulting from the web being incorrectly positioned relative to the surface of the perforated web-braking annular section.

Claims: A suction/braking device for feeding at a constant tension a continuous web of paper or the like, provided in a machine for unwinding a paper web (N, N') from a bobbin (3, 3') between pay-off means (4) and any desired web-using machine, particularly of the type as employed in the tobacco industry, the said device comprising a perforated annular section for braking the speed of a web of paper (N) associated with a stationary suction chamber (12), whereby the speed of paper web (N) which is passing over the annular web-braking section (10) is slowed down by the suction being applied thereon through the suction ports (110) in communication with the suction chamber (12), characterized by the following features: a) the perforated web-braking annular section forms part of a perforated web-braking cylindrical drum (10) which is mounted so as to be rotatable around its axis over a stationary suction chamber (12) formed in the inside of this drum, b) a stationary air-blowing chamber (13) is formed in the inside of the web-braking drum (10) in a substantially diametrically opposite position to the suction chamber (12) for clearing the suction ports (110) in the annular section of the web-braking cylindrical drum (10) peripheral wall, particularly for blowing any paper dust out of the suction ports (110) in the said annular section of the web-braking drum (10) peripheral wall, c) a suction chamber (25) for collection and discharge of any paper dust having been ejected from the suction ports (110) in the annular section of the web-braking drum (10) peripheral wall, is provided on the outside of the web-braking drum (10) close to the air-blowing chamber (13), d) the web-braking drum (10) is operatively connected to a motor (23) for driving the same in rotation, and is rotated around its axis at a very low speed as compared with the speed at which the paper web (N) is caused to slide, preferably in the opposite sense of the web-sliding direction. The device according to Claim 1, characterized in that the web-braking drum (10) is rotatably mounted on a stationary, drum-supporting cylindrical body (11), in which an arcuate suction chamber (12) and an arcuate air-blowing chamber (13) are formed in diametrically opposite lateral positions, with their radially outward open side being closed in a substantially air-tight manner by the peripheral wall of the web-braking drum (10), the suction ports (110) in the perforated annular section of the web-braking drum (10) peripheral wall being alternatingly set in communication with the said chambers while the said drum is being rotated. The device according to Claim 2, characterized in that the drum-supporting cylindrical body (11) is fastened to the one free end side of a coaxial distributor sleeve (14) which by its opposite, other end side is secured to the device frame (9), a suction duct (16) which opens into the suction chamber (12) and is connected to a vacuum generator, and an air-blowing duct (18) which opens into the air-blowing chamber (13) and is connected to a pressure source, such as a compressed air source, being formed in the distributor sleeve (14). The device according to any of the preceding Claims, characterized in that the chamber (25) for collection and discharge of any paper dust having been blown out of the suction ports (110) in the annular section of the web-braking drum (10) peripheral wall is closed in a substantially air-tight manner by the said peripheral wall of drum (10), and is connected to a vacuum generator. The device according to any of the preceding Claims, characterized in that the motor (23) for driving the web-braking drum (10) in rotation is attached to the distributor sleeve (14), while the shaft (123, 20) for driving the said web-braking drum (10) extends through the distributor sleeve (14) and through the drum-supporting cylindrical body (11), so as to be rotatable around its axis. The device according to any of the preceding Claims, characterized in that the suction ports (110) in the perforated annular section of the web-braking drum (10) peripheral wall, are arranged in the fashion of a plurality of circularly arranged parallel rows of ports, a radially projecting, web-guiding annular rim (210) being provided on either sides of the surface of the said perforated annular section of the web-braking drum (10) peripheral wall. The device according to any of the preceding Claims, characterized in that the said device is provided in a machine for unwinding a paper web (N, N') from a bobbin (3, 3'), and is preferably interposed between a paper web (N, N') buffer magazine (2) located downstream of pay-off means (4) and splicing means (5), and any desired web-using machine, particularly of the type as employed in the tobacco industry.

Inventors: PIANA MAURIZIO, PIANA, MAURIZIO
Applicants: SASIB SPA, SASIB S.P.A.
Application year: 1990
Main classification: B65H23
IPC codes: A24C5, B65H23