1. Field of the Invention
The invention relates to a drying roll for drying a fibrous material web, in particular a paper, cardboard or tissue web, in a machine for producing and/or finishing said fibrous material web, which roll can be heated from the inside by a gaseous heat transfer medium, and the internal surface of its jacket is provided with elevations that extend at least essentially radially inwards, the radial height of said elevations being greater than the average radial thickness of the condensate layer that forms on the internal surface of the cylinder jacket during operation, in conjunction with which a way is provided for draining condensate from the condensate chamber that incorporates the areas lying between the elevations.
2. Description of the Related Art
In drying rolls of this kind, steam is used predominantly as the heating medium. The removal of heat during the drying of the fibrous material web results in a phase transition and thus to the formation of condensate. At customary machine operating speeds, a condensate layer forms on the inside of the cylinder jacket as the result of centrifugal force. This condensate layer has high thermally insulating properties and as such impairs the transfer of heat from the steam to the fibrous material web.
Consequently, drying rolls with radially oriented grooves have already been proposed, of which the ribs project to a small extent from the condensate. A drying roll of this kind is previously disclosed, for example, in EP 0 851 059 A1. In this previously disclosed drying roll, the item in question can be, in particular, a Yankee roll with condensate grooves oriented in the circumferential direction. The condensate is sucked directly from the grooves via siphons. The most stable construction possible is believed to be achieved by a special configuration of the ribs.
A drying roll previously disclosed in DE 10 2004017 811 A1 possesses a thin-shelled jacket with reinforcing elements and two jacket layers, in order to avoid deformation in spite of the thin wall thickness.
What is needed in the art is to make available an improved drying roll of the kind mentioned by way of introduction, in which an improved heat transfer and a higher heat flux density are provided, while retaining a simple construction, and which is also capable in particular of being manufactured in an economical manner.
The present invention provides that the condensate chamber or at least one condensate sub-section is in hydraulic contact with at least one front-end region of the cylinder.
In this case, the drying roll can be heated in particular by steam, in conjunction with which the steam chamber can extend, at least in essential respects, over the entire internal space or can consist only of individual chambers, as described in DE 10 2004 017 811 A1, for example.
At least one condensate outflow arrangement can be provided in at least one front-end region of the cylinder.
The condensate outflow arrangement can include a condensate collection channel, which is advantageously oriented in the circumferential direction.
According to an appropriate, practical embodiment of the cylinder according to the invention, at least one siphon is allocated to the condensate collection channel. Outflow of the condensate in this case can be effected, for example, via at least one siphon on each side on which the arriving flow is received.
A further advantageous embodiment is characterized in that a section having a larger internal diameter by comparison with the cylinder jacket adjoins the axial outflow of the condensate axially at least at one end of the cylinder jacket, and in that a corresponding seal is provided on the cylinder jacket. The condensate in this case is spun onto the larger diameter, or else it flows out when at a standstill.
According to a further aspect of the invention, the present invention provides that at least one condensate outflow element for the outflow of the condensate is present in the condensate chamber or in at least one condensate sub-section. A measure of this kind is possible as an alternative to or in addition to the measures concerning the first aspect of the invention.
A condensate outflow element of this kind can include a siphon.
In certain cases, it may also be of advantage for the condensate outflow element to include a small tubular siphon, that is to say a siphon in the form of a small tube. A small tubular siphon of this kind is previously disclosed in EP 0 851 059 A1.
The present invention also provides that the elevations are provided, at least partially, in the form of ribs, between which grooves are formed, and in that the proportion of the width of the groove at the radially external base of the groove to the pitch of the ribs is greater than around 0.1 and smaller than around 0.95. This measure, which also concerns a further aspect of the invention, can in turn be provided as an alternative to or in combination with the measures for at least one of the aspects of the invention described above.
The proportion of the width of the groove to the pitch of the ribs is preferably greater than around 0.3 and smaller than around 0.7.
In particular in the case of a cylinder made of steel, the proportion of the width of the groove to the pitch of the ribs is preferably in the order of around 0.5 to around 0.6.
The elevations can also be provided, at least partially, in particular in the form of bolts. In this case, the proportion of the surface of the cylinder jacket in contact with the condensate to its inner total surface is advantageously greater than around 0.1 and smaller than around 0.95.
According to a preferred practical embodiment, the proportion of the surface of the cylinder jacket in contact with the condensate to its inner total surface is advantageously greater than around 0.3 and smaller than around 0.7. In particular in the case of a cylinder made of steel, this proportion is preferably in the order of around 0.5 to around 0.6.
The condensate outflow device advantageously includes at least one siphon-like element.
It is also particularly advantageous if the elevations, at least partially, possess a cross-sectional form such that the angle formed between the two flanks of a particular elevation is ≧0° and <140°.
The point of intersection at which the tangents of the slope are applied to both flanks or flank sections advantageously lies radially between the elevation in each case and the center of the cylinder.
It is also particularly advantageous if the elevations, at least partially, possess an at least essentially rectangular cross-sectional form. A trapezoidal, parabolic or triangular cross-sectional form in particular is also possible.
According to an appropriate, practical embodiment, the elevations are, at least partially, continuous. Embodiments in particular in which the elevations are interrupted, at least partially, are also possible, however.
The elevations are nevertheless also fundamentally capable of possessing any other cross-sectional form. Circular arcs or even evolvents or rectangles, for example, are thus possible. Generally, however, they will preferably possess an on the whole essentially rectangular or trapezoidal cross-sectional form, and any desired curved forms can be provided for the rounding and transition.
One advantageous, practical embodiment of the cylinder according to the invention is characterized in that the elevations include, at least partially, individual sub-sections, for example radial bolt-like sub-sections, radial rod-like sub-sections and the like. The sub-sections in question can, for example, support the walls in relation to one another and/or also profiles arranged in the longitudinal direction, for example.
The elevations in each case advantageously possess, at least partially, a radial height>2 mm. In this case, their radial height can be in particular >3 mm, appropriately >5 mm and preferably >10 mm.
The optimal radial height of the elevations is dependent on their width, that is to say, for example, the width of the rib, and the radial thickness of the condensate layer in the depression or groove. In this case, the radial height of the section of a particular elevation projecting inwards from the condensate layer is preferably greater than or the same as half of the width of the elevation.
The average radial thickness of the condensate layer is around 3 mm, for example. In this case, the average radial thickness of the condensate layer in question is the average thickness obtained over the total inner surface of the cylinder that is supplied with condensate.
The width of a particular elevation is appropriately around 6 mm.
The radial height of a particular elevation is preferably >6 mm, in particular in the case of such an average radial thickness of the condensate layer of around 3 mm and such a width of a particular elevation of around 6 mm.
For a practical application, the radial height of the elevations for all condensate layer thicknesses encountered in operation should ensure the highest possible heat flux density. For this purpose, according to a preferred practical embodiment of the drying roll according to the invention, the radial height of a particular elevation is greater than or the same as half of the width of the elevation measured at the radially external foot of the elevation, plus a value of around 1 mm.
This radial height of a particular elevation is preferably greater than or the same as half of the width of the elevation measured at the radially external foot of the elevation, plus a value of around 3 mm.
The radial height of a particular elevation is preferably at least 6 mm, in particular in the case of an average radial thickness of the condensation layer of around 3 mm, and a width of the elevation of around 6 mm.
In particular in the case of a one-piece construction of the cylinder jacket provided with the elevations, it is advantageous if the radial height of a particular elevation is <18 mm. Economical manufacture is possible as a result, for example by cutting machining of the elevations, such as by milling, while at the same time retaining good heat flux density.
A distinct improvement is also possible due to the improved heat conduction together with correspondingly good conductivity of the material in the case of a two-piece construction at elevation heights of as little as <18 mm, that is to say having a height as in the case of a steel embodiment, for example. A greater elevation height may be selected, of course, in order to introduce even more heat through the even larger surface. It is fundamentally also able to function, however, with the same height as in the case of a steel embodiment. Elevation heights of >18 mm can be advantageous in particular in the case in which the elevations or ribs consist of a material having a higher thermal conductivity, that is to say, for example, copper, aluminum, alloys, etc.
An advantageous height of the elevation is <30 mm, in particular in the case of a one-piece cast embodiment, taking into account a larger pitch and a larger average rib width that are necessary for the manufacture of the casting.
The pitch of the elevations or ribs is advantageously <100 mm, in conjunction with which it can be appropriately <50 mm, in particular <30 mm and preferably <15 mm.
If the elevations are present, at least partially, in the form of ribs, between which grooves are formed, the proportion of the average groove width to the pitch of the ribs is greater than around 0.1 and smaller than around 0.95. In this case, the expression average groove width is intended to denote the average width produced over the radial extent of the groove.
In one appropriate, practical embodiment, this proportion of the average groove width to the pitch of the ribs is greater than around 0.3 and smaller than around 0.7.
In particular in the case of a cylinder made of steel, this proportion of the average groove width to the pitch of the ribs is appropriately in the order of around 0.5 to around 0.7, and preferably in the order of 0.66.
According to an advantageous, practical embodiment of the drying roll according to the invention, the transition between a particular elevation and the radially external base of an adjoining depression is rounded in each case. If the elevations are present, at least partially, in the form of ribs, between which grooves are formed, the transition between a particular rib and the base of the groove is advantageously also rounded. Given that the area around the transition concerned consequently does not exhibit any sharp edges, a notch effect is prevented, which would otherwise arise, since the cylinder in question is a pressure vessel.
The transition in question advantageously possesses a radius of >1 mm, and preferably >2 mm.
If the elevations are present, at least partially, in the form of ribs, between which grooves are formed, the ribs and the grooves can also be advantageously oriented axially, at least partially, or also in the circumferential direction.
According to an appropriate, practical embodiment, all the ribs and grooves are oriented in an axial direction. As an alternative, it may also be advantageous in certain cases if all the ribs and grooves are oriented in the circumferential direction.
If the ribs and the grooves are oriented, at least partially, in the circumferential direction, the grooves according to a further appropriate embodiment are attached to one another, at least partially, via channels.
In the event that the elevations are present, at least partially, in the form of ribs, between which grooves are formed, at least one condensate outflow element is allocated to each particular groove according to a practical embodiment.
It is also particularly advantageous for at least one siphon to be allocated to each of the particular grooves in question.
If the elevations are present, at least partially, in the form of ribs, between which grooves are formed, the ribs and the grooves can, at least partially, according to a further advantageous embodiment, also be oriented in the form of a spiral, in the form of a coil or in the form of a screw thread.
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
The drying cylinder 10 can be heated from the inside by a gaseous heat transfer medium, in particular such as steam.
The cylinder jacket 12 is provided on its internal surface with elevated sections 14 that extend at least essentially radially inwards. The radial height HE of these elevations 14 is greater than the average radial thickness DK of the condensate layer 16 that forms on the internal surface of the cylinder jacket 12 during operation (see also
The expression average radial thickness DK of the condensate layer 16 is intended to denote the average value of the various thicknesses of the condensate layer that are produced during operation over the entire internal surface of the cylinder jacket 12.
A way, which is described in greater detail below, is provided for the purpose of draining condensate from the condensate chamber that incorporates the areas lying between the elevations 14. The cylinder jacket 12 can define, in whole or in part, the condensate chamber. The condensate chamber can be formed by a single chamber or can be divided into condensate sub-chambers.
The condensate is led away from this condensate chamber or these condensate sub-sections via condensate outflow elements.
The condensate chamber or at least one condensate sub-section is advantageously in hydraulic contact in this case with at least one front-end region of the cylinder (see, for example,
In the present embodiment, the elevations 14 are formed by axially oriented ribs. The interjacent grooves are also oriented accordingly in the axial direction.
As can be appreciated from
The transitions between the grooves 18 and the rib-like elevations 14 can also be similarly rounded in this case. In the present embodiment, the roundings at the free end of the rib-like elevations and the rounded transitions are defined by various radii r1 and r2.
In the various embodiments in
The rib-like elevations 14 in turn possess, for example, a rectangular cross section.
In the present illustrative embodiment, the rib-like elevations 14 possess a trapezoidal cross-sectional form, for example. The transitions between the grooves 18 and the rib-like elevations 14 are similarly rounded, and they are defined here, for example, by the radius r.
The point of intersection at which the tangents of the slope 24 are applied to both flanks similarly lies radially between the elevation 14 in each case and the center 26 of the cylinder (see also
Depicted in
In the embodiments reproduced by way of example in
The rib-like elevations 14 are similarly oriented axially, for example, in this case. The condensate collection channel or groove 30 provided on the inside of the jacket in at least one front-end region 20 of the cylinder is oriented in the circumferential direction.
As can be appreciated from
As previously mentioned, a condensate outflow element of this kind, for example including one siphon or a plurality of siphons, can only be provided in one end region 20 of the cylinder or also in both end regions of the cylinder. In the case of a rotating siphon in particular, a plurality of siphons can be provided appropriately in a condensate channel on the end of the cylinder.
Represented in
Axially oriented, continuous, rib-like elevations 14 are provided in the present case. The interjacent grooves 18 (see
One or also a plurality of small tubular siphons 44 can project into a particular groove 18 for the purpose of draining condensate and discharging it into the condensate collection tube 42. At least one small tubular siphon 44 can be allocated to a particular groove 18 in each case.
The elevations 14 can be present, at least partially, in the form of ribs, between which grooves 18 are formed. The proportion of groove width BNG at the radially external base of the groove to the pitch of the ribs TR is now advantageously greater than around 0.1 and smaller than around 0.95, and preferably greater than around 0.3 and smaller than around 0.7 (see
In the present embodiment, a particular rib-like elevation 14 having an at least essentially trapezoidal cross section possesses a width BEB of around 6 mm at the base, for example, and a width BEE of around 2 mm at the free end, for example. The width of the groove BNG at the radially external base of the groove is around 6 mm, for example. The transitions between the grooves 18 and the rib-like elevations 14 can similarly be rounded, for example. In the present case, the roundings are defined, for example, by a radius r=2.5 mm. Other radii are fundamentally possible, however. The radial height HE of the rib-like elevations 14 lies in a range from around 5 mm to around 10 mm, for example. The pitch TR of the rib-like elevations 14 is 12 mm, for example. The radially external basic section 46 of the cylinder jacket 12, which is adjoined radially inwards by the rib-like elevations 14, possesses a radial height HB in a range from around 20 mm to around 25 mm, for example.
In the present case, the proportion of the groove width BNG to the pitch of the ribs TR is around 0.5, for example, which is advantageous in particular for a drying roll 10 made of steel.
The width of a particular elevation 14 is indicated with “BE”, and the radial height of a particular elevation 14 is similarly indicated with “HE”. The radial thickness of the condensate layer that is formed on the inside of the cylinder jacket 12 is indicated with “DK”.
At the same time, the following equation should preferably be applied for the indicated quantities, and in particular where the ribs are made of steel:
Steel exhibits very poor heat transfer compared with aluminum or copper. Consequently, a large rib height does not make much sense in this case. A certain rib width is required, however, in order to lead through the energy.
In particular, the average thickness of the condensate layer may similarly be taken as the thickness DK of the condensate layer 16.
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 |
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20 2005 020 588.5 | May 2005 | DE | national |
20 2005 020 589.3 | May 2005 | DE | national |
10 2006 015 796.6 | Apr 2006 | DE | national |
This is a continuation of PCT application No. PCT/EP2006/061868, entitled “DRYING ROLL”, filed Apr. 27, 2006, which is incorporated herein by reference.
Number | Date | Country | |
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Parent | PCT/EP2006/061868 | Apr 2006 | US |
Child | 11931221 | US |