Advancing material of indeterminate length – With adherence or attraction of material to advancing means – By pneumatic pressure
Reexamination Certificate
1999-08-10
2001-07-03
Mansen, Michael R. (Department: 3653)
Advancing material of indeterminate length
With adherence or attraction of material to advancing means
By pneumatic pressure
C226S091000, C226S012000, C162S193000, C162S367000
Reexamination Certificate
active
06253983
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a vacuum conveyor for guiding a running web, e.g., a lead strip (or “threading tail”). Such a vacuum conveyor is used for transporting a web, e.g. a paper and cardboard web, from a section of a paper-making or paper-finishing machine to a following section of that machine.
2. Discussion of Background Information
A vacuum conveyor is known from DE 26 36 887 which is similar to U.S. Pat. No. 4,022,366. Conveyors of this kind have proven successful in operation. In some applications, however, a paper tail must be transferred from a vacuum conveyor to a rope nip (of a following machine section) at a very high speed (over 1500 meters/min). This requires a very rapid change of degree of the vacuum applied to the conveyor. For this purpose it is known to use a pneumatic operated damper at the vacuum source or in the vacuum line.
Recently, however, the operating speed of paper-making or paper-finishing machines is being further increased, namely up to about 2200 meters/min. Unfortunately, in such extreme high speed systems, the conventional dampers do not operate in a reliable manner.
SUMMARY OF THE INVENTION
Therefore, the invention is based on the problem of further developing the known vacuum conveyor and its vacuum control in such a way that the transfer of a tail into the ropes of a following machine section is improved, in particular at extremely high operating speeds.
In particular, the vacuum control of the instant invention includes an air-permeable endless conveyor belt that is tensioned over at least two rolls, and in which a suction box is located within the loop of the conveyor belt and is connected to a vacuum source. Further, at least one of the rolls can be driven to allow the endless conveyor belt to travel over the rolls and the suction box, so that the vacuum propagates through the run of the conveyor belt running in the direction of web travel, which draws the web to be guided onto the conveyor belt by suction. A vacuum control is adapted to establish a fast decrease of the vacuum degree in the suction box and includes a movable element positioned at an inner surface of a wall of the suction box. The wall has an aperture which may be closed by the movable element. An actuator is connected to the movable element such that, in an active state, the actuator causes movable element to close the aperture.
According to the present invention, a wall of the suction box has an aperture which may be closed by a movable element placed at the inner side of the wall. An actuator is connected to the movable element for pressing the same onto the inner side of the wall, if one desires to close the aperture, i.e. if the vacuum conveyor is in its normal operating state. In this state, the atmospheric pressure is working onto the outer side of the movable element and wants to remove the movable element from the wall (whereby the aperture would be opened). However, onto the inner side of the movable element, two forces A and B are effective against the atmosperic pressure for maintaining the aperture closed.
Force A is a variable control force or “actuator force” created by the actuator and force B is depending upon the internal pressure existing in the interior of the suction box, which is the difference between the atmospheric pressure and the actual vacuum degree. The higher the vacuum degree is, the smaller force B is. The vacuum control according to the present invention will operate in the following way: If, e.g. during a start-up of a paper-making machine, the tail of a lead strip of the paper web arrives at the vacuum conveyor for further transferring the lead strip into a rope system of a following machine section, the lead strip covers the suction openings (e.g. slots) of the conveyor. As a result the internal pressure in the suction box severely decreases, thus, preventing the lead strip from being held too firmly to the conveyor. However, the decrease of the internal pressure immediately results in a decrease of the force B, whereby the aperture, if force A had been adjusted to a relative low set value is quickly opened. Now as vacuum decreases (i.e. the internal pressure increases), the movable element again closes the aperture. Thus, a steady and relatively low vacuum degree (which is dependent upon the set value of force A) is created within an extremely short period of time. Such a rapid change of the vacuum degree (in the vacuum conveyor) will improve the transfer of the lead strip, in particular when the tail of the lead strip must be transferred into a rope system of the following machine section (e.g. calender or coating machine or reel) of a high-speed paper-making or -finishing machine.
The present invention is directed to an apparatus for guiding a running web that includes at least two guide rolls, which at least one driven roll, a suction box coupled to a vacuum source and having a wall having an aperture, an air-permeable belt tensioned over the at least two rolls, and the suction box being positioned within a loop formed by the belt. The suction box is positioned to suction to a portion of the belt that is adapted to guide the running web. The apparatus also includes a vacuum control adapted to control a degree of vacuum in the suction box that includes a movable element position adjacent the aperture and an inner surface of the wall. The moving element is adapted to open and close the aperture, and an actuator is coupled to the movable element to effect the opening or closing of the aperture.
According to a feature of the instant invention, a stationary element can be located within the suction box. The apparatus can also include a pressure source and a control line, and the actuator can include an air bag positioned between the stationary element and the movable element. A control valve can be adapted to adjustably establish a substantially constant pressure in the air bag, and an interior of the air bag may be coupled to the pressure source through the control line. Further, the control valve may be a self-relieving valve. Further still, an additional valve may be coupled to the control line which selectively couples the actuator to one of the pressure source and an outside atmosphere. Moreover, the movable element can include a plate which is coupled to the air bag, so that the plate can be adapted to contact the inner surface to close the aperture.
In accordance with another feature of the instant invention, the movable element may have an outer side adapted to be exposed to an outside atmosphere, and an inner side adapted to be exposed to an actuator force and a vacuum force within the suction box. When the actuator force and the vacuum force within the suction box is greater than the outside atmosphere, the movable element closes the aperture, and when the actuator force and the vacuum force within the suction box is less than the outside atmosphere, the movable element opens the aperture.
According to still another feature of the present invention, the running web can include a paper web. Further, the running web can include a threading strip adapted for threading the web through a machine. Still further, the running web can include a threading strip for a paper web adapted for threading a paper web through one of a production, finishing, and processing a machine.
In accordance with a further feature of the invention, the suction box may be pivotably positionable.
The present invention is also directed to an apparatus for guiding at least a portion of a paper web. The apparatus includes at least two guide rolls, which includes at least one driven roll, a suction box, which includes an apertured wall and which is coupled to a vacuum source, and an air-permeable belt guided around the at least two rolls and the suction box. The suction box is positioned to suction a portion of the belt. A vacuum control device is adapted to control a vacuum within the suction box, and includes a movable element located within the suction box and positioned adjacent the apertured wall. An ac
Greenblum & Bernstein P.L.C.
Mansen Michael R.
Voith Sulzer Papiertechnik Patent GmbH
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