Patent Application
20090211723
1. Field of the Invention
The invention relates to a pressure hood with a pressure hood body to be used in conjunction with especially a heated cylinder in a machine for the production and/or conversion of a fibrous web, especially a paper-, cardboard- or tissue web, and a seal assembly to seal said pressure hood body against the cylinder.
2. Description of the Related Art
A pressure hood of this type is essentially known and is used for example in a dryer for the continuous drying of a fibrous web coming off the outer circumference of a heated cylinder. Due to the heat released from the cylinder to the fibrous web, moisture evaporates from the fibrous web and is absorbed by at least one wire or fabric which travels together with the fibrous web and which lays on the fibrous web on the side of said web facing away from the cylinder.
A belt, i.e. a steel belt, follows on the side of the wire or fabric facing away from the fibrous web against which a pressure medium which is located inside the pressure hood exerts pressure. In order to seal the pressure hood against the cylinder—in other words, in order to avoid the pressure medium escaping from the interior of the pressure hood—a seal assembly is provided. This is equipped with seals progressing in lateral direction, in other words in the circumferential direction of the cylinder and transversely to the direction of web travel, in other words parallel to the cylinder axis, and which are movable in radial direction and are pressed against the moisture impermeable belt.
The seals drag on the moisture impermeable belt and are subject to especially high wear and tear because of the sliding friction that exists between the seals and the moisture impermeable belt. Consequently, the seals have to be renewed or, respectively replaced often. Traditionally the entire pressure hood must be removed from the cylinder for this purpose, or the seal assembly must be constructed so that it can be disassembled and must be taken apart which, respectively causes considerable assembly work directly at the machine. This is not only expensive, but also time consuming, so that expensive down times are caused by the seal replacement.
What is needed in the art is a pressure hood which permits a simpler and faster replacement of the seals.
The present invention provides a pressure hood with a pressure hood body to be used in conjunction with especially a heated cylinder in a machine for the production and/or conversion of a fibrous web, especially a paper-, cardboard- or tissue web, and a seal assembly to seal said pressure hood body against the cylinder, wherein the seal assembly can be inserted into or removed from the pressure hood body through a movement in axial direction relative to the pressure hood body, which is located in particular on the cylinder.
In this context the term “in axial direction” is to be understood to be always parallel to the rotational axis of the cylinder, whereas a “radial direction” always progresses at right angles to the rotational axis of the cylinder. The term “in circumferential direction” refers in this context to the circumference of the cylinder.
The invention is based on the general concept that the seals, for example sealing strips, are not mounted individually on the pressure hood, but are instead collectively assembled in a seal assembly which can be slid into or out of the pressure hood as an entirety for the purpose of replacing or exchanging the seals, without having to remove the pressure hood from the cylinder for this purpose.
Once the seal assembly has been slid from the pressure hood the individual seals are easily accessible and can be exchanged easily and quickly. This shortens the machine down time associated with a seal replacement or exchange, resulting in a more economical operation of the machine including the cylinder and the pressure hood.
The machine down time can still be further reduced if two seal assemblies are available, whereby a first seal assembly is inserted in the machine and a second seal assembly with perfect seals is held in reserve. This allows the first seal assembly to be removed from the pressure hood when the seals in the first seal assembly are worn, and to immediately insert the second seal assembly containing the perfect seals into the pressure hood. This reduces machine down times simply to the amount of time which is required to remove and to insert a seal assembly into the pressure hood. While the machine operates with the second seal assembly, the worn seals in the first assembly can be removed and replaced without any time pressure.
According to one design variation the seal assembly includes a seal support which is movable in axial direction relative to the pressure hood. The seal support supports the actual seals, which are in the embodiment for example of sealing strips.
The seal support may include two curved sections extending in circumferential direction, which are connected with each other, especially in the area of their ends, through an axial segment extending in axial direction. In other words the seal support is in the embodiment of a rectangular frame which is curved to follow the shell surface of the cylinder or the inside of the pressure hood respectively.
In an effort to improve the rigidity, especially the torsional rigidity the curved segments can additionally be connected with each other through at least one brace-type reinforcing element.
In order to achieve reliable control of the seal support over its entire travel path the seal support can—in the area of its axial segments—be guided along the pressure hood body.
According to an additional design variation spacer devices are provided in order to keep the seal assembly during its movement relative to the pressure hood body at least partially at a distance. On the one hand this reduces the friction between the seal support and the inside of the pressure hood body which occurs during the movement of the seal assembly, thereby reducing the force necessary for moving the seal assembly. On the other hand it prevents that a seal, for example a sealing ring located between the seal support and the inside of the pressure hood body is damaged.
Forces or movements respectively can be exerted through the spacer devices in radial direction and/or in tangential direction upon the seal assembly. Through a suitable combination of radial and tangential forces or tangential movements the large surface of the seal assembly can be kept at a distance from the inside of the pressure hood body.
In addition the spacer devices can be located in an area of axial segments of a seal support of the seal assembly. Through an appropriate application of radial and tangential forces or movements upon the axial segments, the seal support can be compressed radially, and also at the same time be activated in circumferential direction, so that the curved sections of the seal support can be held at a distance, essentially over their entire length to the inside of the pressure hood body.
According to one design variation the spacer devices can include at least one guide extending in axial direction and at least one roll- or glide element which is guided by the guide, whereby the guide is contoured to cause a movement in certain places in radial direction of the roll or glide element. Due to the contour in the guide a radial force or respectively movement can be exerted especially easily upon the axial segments of the seal support through the combined effect of guide and roll- or glide element.
The guide can be mounted on the pressure hood body and the roll- or glide element can be installed on the seal support. Basically however, an opposite arrangement is also feasible where the guide is mounted on the seal support and the roll- or glide element is installed on the pressure hood body.
According to an additional design variation at least one guide is equipped in addition with one contour, especially grooves with descending and/or ascending ramps causing the roll or glide element in certain places to move in circumferential direction. The contour based movement of the roll or glide element in circumferential direction represents a simple method of exerting a tangential force or respectively movement upon the seal support and contributes to holding the seal assembly at a distance to the inside of the pressure hood body.
Alternatively, or in addition to a contour of this type at least one guide can be mounted on the pressure hood body, movably in circumferential direction relative to the pressure hood body. A guide of this type for example can be moved by way of a pneumatically or hydraulically inflatable pressure tube or also manually in circumferential direction.
According to an additional design variation especially a single- or multistage seal is provided all around on one side of the sealing assembly facing away from the pressure hood body. The seal seals the interior of the pressure hood vis-à-vis the cylinder, or respectively vis-à-vis a moisture impermeable belt which is routed around the cylinder. Especially a multistage seal can effectively prevent leakage from the pressure hood of a medium which is pressurized inside the pressure hood.
The seal can include a sealing strip and especially several sealing strips located parallel to each other. Each of the parallel positioned sealing strips represents a sealing stage of a multistage seal. The sealing strip or each sealing strip can be placed in a groove that is provided in a seal support of the seal assembly.
According to an additional design variation the pressure of the sealing strip or of each sealing strip acting against the cylinder is adjustable. This permits a desired sealing result to be adjusted and to be maintained when the sealing strips begin to wear.
For example a pressure tube can be provided to adjust the pressure exerted by the sealing strips. By supplying the pressure tube with a suitable pressure fluid, for example compressed air, compressed water, compressed oil, etc., the pressure tube can be inflated in order to activate the associated sealing strips for the purpose of adjusting the desired pressure force.
The pressure tubes can in particular—always with associated sealing strips—be supplied independent from each other. According to an additional design variation each pressure tube forms in particular a closed ring. This can be produced for example by flush gluing together of the tube ends.
The pressure tube can have a bellows-type cross section, at least in sections. In addition, two opposite side walls of the pressure tube can be connected with each other by at least one cross link, whereby in a cross sectional view at least two pressure tube chambers are formed. This pressure tube geometry ensures an especially large stroke and at the same time especially smooth running during expansion of the pressure tube, thereby on the one hand enabling increased permissible wear and tear—that is in other words a longer service life of the seal—and on the other hand a more sensitive response to a change in the pressure force.
According to an additional design variation a first canal for the removal of pressure medium from a space that is defined by a first and a second sealing strip—viewed from the interior of the pressure hood toward the outside—is provided. Through this canal pressure medium which has escaped past the first sealing strip from the inside of the pressure hood can be removed The removed pressure medium can be collected and/or returned via an appropriate line into a storage tank or respectively again into the inside of the pressure hood.
In addition a second canal for the removal of pressure medium from a space that is defined by a second and third sealing strip—viewed from the interior of the pressure hood toward the outside—can be provided. With the sealing assembly completely inserted into the pressure hood body the second canal can be connected, for example with a suction device, thereby preventing the leakage of pressure medium from the pressure hood even more effectively.
According to an additional design variation the sealing strip or each sealing strip is composed of several sealing strip segments which are movable relative to each other at their joint. Adjoining sealing strip segments may have extensions on their ends facing each other which engage tongue and groove fashion with each other.
Due to the movability of the sealing strip segments a length adjustment is created, which is necessary especially when the sealing strips which extend in circumferential direction have to be adjusted to a changing radius because of wear and tear. A length adjustment is also advantageous on the sealing strips which extend in axial direction, since the sealing strips and the seal support typically have different heat expansion coefficients and therefore experience different length changes if they absorb different temperatures during machine operation. Lastly, the length adjustment prevents distortions of the sealing strips in the seal support and ensures smooth running of the seal, that is of the contact pressure of the sealing strips in radial direction.
In order to avoid damage during pressure contact to the pressure tube which could result due to a reduced contact surface at the joint locations, the joint location could be provided with a cover at the side of the pressure tube. For example they could be covered by thin plates.
According to an additional design variation ways are provided to prevent especially a sealing strip segment which is located in a curved segment of the seal support from moving in longitudinal direction of the sealing strip segment, relative to the seal support. In this way correct positioning of the sealing strip segments, especially of the sealing strip segments extending in circumferential direction, is permanently ensured.
The ways may for example include a pin-type element extending transversely through the sealing strip segment which is secured on the seal support to prevent a movement in longitudinal direction of the sealing strip segment. The pin-type element may be movable in radial direction relative to the seal support, so that the desired contact pressure can also always be adjusted with a sealing strip which extends in circumferential direction. The pin-type element may be in the embodiment of for example a bolt, a pin or a screw.
According to an additional design variation a seal is provided all around on a side of the seal assembly facing the pressure hood body. This ensures that the seal assembly when inserted into the pressure hood body is sealed vis-à-vis the pressure hood body. The seal may for example include especially a closed seal ring, for example in form of an O-ring, packing or a pneumatic tube.
An additional subject of the invention is also an arrangement including a pressure hood of the type previously described and at least one change-over rack to accommodate a seal assembly that was removed from the pressure hood body or one that is to be inserted into the pressure hood body. The change-over assembly serves to support the seal assembly in its removed state and contributes to a simpler and faster exchange of the worn seals.
The change-over rack can be designed such and can be located relative to the pressure hood such that the seal assembly can be accommodated by the change-over rack simultaneously with its removal from the pressure hood body. In this way the change-over rack can be positioned at the pressure hood body so that the seal assembly, when it is slid from the pressure hood body, is immediately slid into the change-over rack and that after checking or respectively replacement of the seal in the change-over rack is again slid into the pressure hood body. During the process of sliding the seal assembly in and/or out, the change-over rack can be connected with the pressure hood body, especially through screws and/or clamps.
In order to reduce the machine down time even further and to simplify the replacement of seals even further, two change-over racks may be provided, whereby the one change-over rack is provided to receive a first seal assembly that is to be removed from the pressure hood body, and the other change-over rack carries a second seal assembly to be inserted into the pressure hood body in place of the first seal assembly. Immediately after sliding the first seal assembly from the pressure hood body, the second seal assembly can therefore be inserted into the pressure hood body and machine operation can be resumed. While the machine operation is continued with the second seal assembly, the worn seals from the first seal assembly can be renewed or replaced, thereby preparing the first seal assembly for renewed service in the pressure hood.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
Referring now to the drawings, and more particularly to
A pressure hood 11 with a pressure hood body 12 is mounted on the cylinder. Viewed in axial direction the pressure hood body envelopes the circumferential surface of the cylinder 10 essentially over the entire width and viewed in circumferential direction to approximately three quarters of the cylinder circumference. The interior of the pressure hood 11 can be filled with a pressure medium, for example with water which can have an overpressure of several bar relative to the surroundings in order to press against the cylinder 10 a moisture impermeable belt 13 (
In order to seal the pressure hood 11 against the moisture impermeable belt 13, a seal assembly 14 is provided which is movable in axial direction relative to the pressure hood body 12. With the pressure hood body 12 mounted on the cylinder 10 the seal assembly 14 can be slid in and out of the pressure hood body 12 in a gap formed between the pressure hood body 12 and the cylinder 10, in order to exchange or replace worn seals.
A change-over rack 16 is provided for the retention of the seal assembly 14 after its removal from the pressure hood body 12. It is designed that it can be positioned relative to the pressure hood 11 so that the seal assembly 14 glides directly from the pressure hood body 12 into the change-over rack.
In order to keep the down time of the machine which includes the cylinder 10 and the pressure hood 11 as short as possible during a replacement of the seals, two same-type change-over racks 16 and seal assemblies 14 may be utilized, whereby always one functional seal assembly 14 is inserted into the pressure hood body 12, and at the same time always the other seal assembly 14, after replacement of its seals, is held in reserve for an exchange with the one seal assembly 14.
As illustrated in
On one outside 26 of the seal support 18 facing toward the pressure hood body 12, a closed sealing ring 28, for example a O-ring, packing, a pneumatic tube or similar device is inserted into a correspondingly continuous groove 30 (
As can be seen in
The sealing strips 36, 38, 40 are inserted into the grooves 34 in such a way that they can be pressed against the moisture impermeable belt 13 through a movement in radial direction.
For the purpose of pressing the sealing strips 36, 38, 40 against the belt 12, pressure tubes 42 are provided which are inserted in the grooves 34 and which exhibit a bellows-like cross section and which can be expanded through applying a suitable pressure fluid, for example compressed air, compressed water, compressed oil, etc. in order to seat the sealing strips 36, 38, 40 in radial direction.
The sealing strips 36, 38, 40 are stationary relative to the moisture impermeable belt 13 running over the cylinder 10. They are therefore dragging seals. With this type of seal it cannot be avoided that pressure medium can escape from the interior of the pressure hood 11—the so-called pressure chamber 44. Moreover, the first sealing strip 36—when viewed from the interior of the pressure hood 11 toward the outside—causes a pressure drop, so that the pressure medium collecting in the first gap 46 between the first sealing strip 36 and the second sealing strip 38 has a reduced pressure, perhaps only half as high, compared to the pressure medium in pressure chamber 44.
A discharge canal 48 is provided in the seal support 18 for the purpose of removing the escaped pressure medium from the first gap 46. The discharged medium can be collected and respectively led back into the pressure chamber 44. In order to increase the volume of the first gap 46, an additional groove 50 is built into the seal support 18.
In order to even more effectively prevent leakage of pressure medium from the pressure hood 11 a third sealing strip 40 is provided in addition to the first and the second sealing strips 36, 38, thereby providing a total of a three-stage seal. Basically it is however also possible to provide a seal with a number of sealing strips that differs from the three aforementioned.
The second sealing strip 38 and the third sealing strip 40 define a second gap 52. The second gap 52 is connected with a second discharge canal 54 in the seal support 18 which, when installed in the pressure hood body 12 of the seal assembly 14 can be connected with a suction device with which the pressure medium that collects in the second gap 52 can be sucked away.
The sealing strips 36, 38, 40 are always composed of several sealing strip segments which are movable relative to each other at their connecting locations.
Due to the movability of the sealing strip segments 56 relative to each other a length adjustment is created, which is necessary especially when the sealing strips which progress in circumferential direction have to be adjusted to a changing radius because of wear and tear. A length adjustment is however also advantageous on the sealing strip segments 56 extending in axial direction, since the sealing strips 36, 38, 40 and the seal support 18 have different length expansion coefficients due to different materials and therefore can experience different length changes if they absorb different temperatures during machine operation. Lastly, the hereby created length adjustment prevents distortions of the sealing strips 36, 38, 40 in the seal support 18 and ensures smooth contact pressure of the sealing strips 36, 38, 40 in radial direction.
In order to avoid damage of the pressure tube 42 which is allocated to a sealing strip 36, 38, 40 which could result due to a reduced contact surface at the joint locations between the individual sealing strip segments 56, thin cover plates 60 are arranged in the area of the joint location, between the sealing strip segments 56 and the associated pressure tube 42.
In order to prevent the individual segments 56 of the sealing strips 36, 38, 40 which are inserted into the curved segments 20 of the seal support 18 from shifting in circumferential direction, said sealing strip segments 56 are secured by a bolt 62 extending transversely through them and which is located movably in a recess 64 of the curved segment 20, extending in radial direction. In order to achieve optimum movability of the bolt 62 inside the recess 64, the bolt 62 is always positioned in a sliding block 66 that is inserted in the recess 64. Basically however, the bolt can also be used feasibly without sliding components. The sealing strip segments 56 can always be twisted around their bolt 62.
The glide component 66 serves essentially to enlarge the contact surface in the recess 64 and does not necessarily have to be an individual component, but can also be represented by the bolt 62 itself, for example through a flattened two-edged or square head.
According to an additional design variation the bolt 62 may be in the form of a special screw with a square head on the one side (glide component 1), a locating/sealing surface in the area of the sealing strip segment 56 and an outside thread on the other side on which a square nut (sliding component 2) is located. Passage of the pressure water through the sealing strip segment 56 via the locating/sealing surface can be impeded by additional ways, for example an O-ring seal.
Because of the movability of the bolts 62 in the recesses 64 which extend in radial direction, a reliable contact pressure of the sealing strip segments 56 in radial direction upon the cylinder 10 is ensured, even when the seals begin to wear.
It is however also conceivable to have a roll with an outward facing V-shaped profile run in an inside edge, for example in a notch or slot. In principle, rolls having a cylindrical, conical or ball-shape are feasible. In addition the support may occur through several rolls, located in different—preferably vertical relative to each other—directions.
In order to create an impermeable as possible connection in this situation between the seal assembly 14 and the pressure hood body 12 with regard to the pressure medium on the inside of the pressure hood 11, the seal support 18 can be mounted on the pressure hood body 12 by way of a screw connection and/or a clamp connection.
On opposite sides of this screw, grooves 96 are provided in the opposing support 94 in which pressure tubes 98 that are supplied with pressure fluid are located. The grooves 96 are enclosed by support strips 100 which support themselves on the outside of the pressure hood 12 and which extend at least partially into the grooves 96.
In order to secure the seal assembly 14 onto the pressure hood body 12 the pressure tubes 98 are supplied with pressure fluid, thereby causing the pressure tubes 98 to expand. Due to their expansion the pressure tubes 98 which support themselves on the support strips 100 seat against the opposing support 94 in radial direction toward the outside, thereby pulling the second profiled strip 90 toward the outside over the screw which is not illustrated. This movement of the second L-shaped profiled strip 90 causes also the axial segment 22 of the seal support 18 to be pulled toward the outside over the first L-shaped profile strip 86, thereby pressing it against the pressure hood body 12.
The first L-shaped profile strip 86 and the second L-shaped profile strip 90 are located in a groove 102 of the pressure hood body 12 which extends in axial direction and whose cross section is selected such that the profile strips 86, 90 have sufficient clearance to pull the seal support 18 to the pressure hood body 12, however have practically no clearance viewed in circumferential direction in order to prevent a movement of the axial segment 22 in circumferential direction relative to the pressure hood body 12 through which the profile strips 86, 90 can disengage.
Securing of the seal support 18 by way of the clamp connection on the pressure hood body 12 has the advantage that no screws have to be actuated. The clamp connection is therefore especially suitable for use in areas that have poor access.
When sliding the seal assembly 14 into the pressure hood 11 or respectively when sliding the seal assembly 14 out of the pressure hood 11 it is advantageous if there is a radial distance between the seal support 18 and the pressure hood body 12, in order to keep friction low on the one hand, and as not to damage the static sealing ring on the other hand.
In order to create such a radial distance between the sealing assembly 14 and the pressure hood body 12, the seal support 18 is deformed to a smaller radius through forces or respectively movements which are effective in radial and tangential direction, as indicated in
In order to generate these forces, or respectively movements, a contour is provided in the upper edge area 80 of the guide 72 illustrated in
Similar to the guide 72 in
In order to produce a distance between the seal assembly 14 and the pressure hood 12, in other words in the area of both axial segments 22 of the seal support 18, an inward directed radial force or respectively movement 104 is exerted upon the seal support 18 (
While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2006 051 392.4 | Oct 2006 | DE | national |
This is a continuation of PCT application No. PCT/EP2007/058527, entitled “PRESSURE HOOD HAVING A REMOVABLE SEALING APPARATUS”, filed Aug. 16, 2007, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2007/058527 | Aug 2007 | US |
| Child | 12420221 | US |
