CA2026897A1 - Doctor bar for the volumetric metering of flowable materials onto a travelling web - Google Patents
Doctor bar for the volumetric metering of flowable materials onto a travelling webInfo
- Publication number
- CA2026897A1 CA2026897A1 CA 2026897 CA2026897A CA2026897A1 CA 2026897 A1 CA2026897 A1 CA 2026897A1 CA 2026897 CA2026897 CA 2026897 CA 2026897 A CA2026897 A CA 2026897A CA 2026897 A1 CA2026897 A1 CA 2026897A1
- Authority
- CA
- Canada
- Prior art keywords
- rises
- doctor bar
- web
- bar
- doctor
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Abandoned
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C—APPARATUS FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05C11/00—Component parts, details or accessories not specifically provided for in groups B05C1/00 - B05C9/00
- B05C11/02—Apparatus for spreading or distributing liquids or other fluent materials already applied to a surface ; Controlling means therefor; Control of the thickness of a coating by spreading or distributing liquids or other fluent materials already applied to the coated surface
- B05C11/023—Apparatus for spreading or distributing liquids or other fluent materials already applied to a surface
- B05C11/025—Apparatus for spreading or distributing liquids or other fluent materials already applied to a surface with an essentially cylindrical body, e.g. roll or rod
-
- D—TEXTILES; PAPER
- D21—PAPER-MAKING; PRODUCTION OF CELLULOSE
- D21H—PULP COMPOSITIONS; PREPARATION THEREOF NOT COVERED BY SUBCLASSES D21C OR D21D; IMPREGNATING OR COATING OF PAPER; TREATMENT OF FINISHED PAPER NOT COVERED BY CLASS B31 OR SUBCLASS D21G; PAPER NOT OTHERWISE PROVIDED FOR
- D21H23/00—Processes or apparatus for adding material to the pulp or to the paper
- D21H23/02—Processes or apparatus for adding material to the pulp or to the paper characterised by the manner in which substances are added
- D21H23/22—Addition to the formed paper
- D21H23/52—Addition to the formed paper by contacting paper with a device carrying the material
- D21H23/56—Rolls
- D21H23/58—Details thereof, e.g. surface characteristics, peripheral speed
Landscapes
- Coating Apparatus (AREA)
- Paper (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
A doctor bar for volumetric metering of a flowable coating material onto a paper or cardboard web has an elongated body whose generally cylindrical periphery is defined by a surface distribution of discrete rises separated by troughs. Therises have outer faces lying in an imaginary surface coaxial with the body and which are straight in axial cross section. The total area of the faces constitutes 10% to 50% of the area of the cylindrical imaginary surface and the profile depth of the rises is between 30µm and 150µm.
A doctor bar for volumetric metering of a flowable coating material onto a paper or cardboard web has an elongated body whose generally cylindrical periphery is defined by a surface distribution of discrete rises separated by troughs. Therises have outer faces lying in an imaginary surface coaxial with the body and which are straight in axial cross section. The total area of the faces constitutes 10% to 50% of the area of the cylindrical imaginary surface and the profile depth of the rises is between 30µm and 150µm.
Description
17~'`4 2 ~ 9 ~
~CIOR BAR FOR THE VOLUMETRIC I~TERING OF FLOWABLE
MATERL~LS ONI O A TRAVELLING WEB
SPECIFICATION
Fie~d of the ~nvention Our present invention relates to a doctor bar for the volumetric rnetering of coating materials, for example, glue or coloring fluids, onto travelling webs, for example, of paper or cardboard. The invention also relates to a coating apparatus using the improved doctor bar as a metering element for the coating material.
Background Qf thç LTIvention - -In the coating of travelling paper or cardboard webs, it is known to pro~ide a doctor bar having circumferential grooves defining on the bar, lands separated by the troughs defining the grooves. Such doctor bars are utilized for applying coloring or glue films to the surface of the web or for coating the web with pr~deterrnined quantities of the ~owable coating agent, the amount of which is ini~uenced by the groove cross section of the doctor bar.
The doctor bar can be applied directly to the web, if the coating material is applied thereto directly at an upstream location so that the doctor bar senes tocontrol the coating weight per ULUt area Alternatively, the doctor bar can function to control the quanti~ of the coating applied to a coating drum which tran~fe~ the coating liquid to the web. In that case, the doctor bar is provided downstream of the applicator in the direction of rotation of the transfer or coating roller or drum.
' 2 ~ 8 ~ 7 In that case, the doctor bar is provided downstream of the applicator in the direction of rotation of the transfer or coating roller or drurn.
In the case in which a roller or drum is underslung or overslung by the web, the applicator and metering doctor bar can be provided in succession in the path of S this roller or web. In the case of another coating system in which the web passes between rollers, one or both of the rollers can form transfer rollers as described and cooperate with applicators and doctor bars for controlling the flowable coating material applied to one or both of the rollers before the roller or rollers transfer the coating material to the web.
Doctor bars of conventional design are ~ound in such applications in German Open Application DE-OS 37 35 889 and in German Utility Model DE-GM 84 14 413. In~he first case, the doctor bar cooperates direct~y with the paper web whereas inthe second case the doctor bar serves to control the application of a film to a ~ansfer roller whicb, in the nip between two rollers, applies the coating material to the web.
It has been found that doctor bars in which the groove arrangement was formed by wrapping a wire around a cylindrical body, suffered from rapid wear. If eflorts are made to use rubber coated rollers in coniunction therewith, it is difficult to maintain constant conditions and there is a danger of darnage to the roller surface.
2û In German Patent Document DE-OS 38 41 494 a doctor bar is described which has a multiplicity of button-lL~ce protuberances along the surface. These can be fab-ricated by machining recesses in a cylindrical bar, by etching, milling, grinding, pressing, etc. The protuberances or the entire doctor bar can be composed of lowwearing materials, for example, hard materials such as titanium or tungsten, hard chromed steel, glass or oxide ceramic materials.
Notwithstandirlg the well developed character of this prior art, however, efforts to provide low wearing doctor bars capable of producing stripe-free thincoatings of coating liquids s,. the type descn~d on travelling webs, especiaiiy of ~2~8~7 paper or cardboard, have not been fully satisfactory. Furtherrnore, when the doctor bar was employed for applying coatings to ~ansfer rollers, damage to the transfer roller could not be excluded in many cases.
Objects of ~he Inventio~
It is, therefore, the principal object of the present invention to provide an improved doctor bar capable of stripe-free application of small-thickness coatings to travelling webs, especially of paper or cardboard, whereby the drawbacks of earlier systems are a~oided.
Yet another object of the invention is to provide a doctor bar which can be utilized effectively for the application of transferable coatings to a transfer roller without damage to the surface of this roller.
St;~l another object of the invention is to provide an improved apparatus for coating paper and cardboard webs having an irnproved doctor bar.
Summa~of the Invention These objects and others which will become apparent hereinafter are attained, in accordance with the invention in a doc~or bar for volumetric metering of a flowable coating material onto a web, especi~lly a paper or cardboard web, comprising an elongated body formed with a generally cylindrical periphery defined by a surface distribution of discrete rises separated by troughs, the rises having outer faces Iying along a cylindrical surface coaxial with the body and beirlg straight in alcial cross section;
a total area of the faces constituting 10 5'o to 50 % of the area of the cylindrical periphely; and a profile depth Pt(2.5mm) of the cylindrical periphery being between 30 ~ m and 150 ~m according i~ ~ennan Industrial Standard DIN 4771.
- l~q4 2~ 897 According to a feature of the invention each of the rises has flanks extending from the respective outer face to a ~loor of an adjacent trough, said flanks having a roughness depth Rt which is a maximum of 10 ~ of the profile depth Pt(2.5mm).
S Preferably the geometric dimensions and distributions of the rises varies along the cylindrical periphery randornly within predeterrnined limits.
According to a feature of the invention, the rises are generally elongated in a circumferential direction of the body, have widths b of substantially lO ~ m to lOO~m, and have spacings of substantially 1501sm to 400~m from one another.
The rises can have widths b randornly varying between substantially 10 ~ m and substantially 100 ~ m, and spacings randomly varying between substantially lSO~m to substantially 400~m from onç another.
The lengtbs of the rises extendin~ in the circurnferential direction can be between substantially lmm and lSmr~L
AdvaIltageously, the troughs defîne in a central longitudinal section through the doctor bar, an open cross sectional area between the rises on one side of the bar amounting to lS mm2 to 80 mm2 per meter of the length of the bar.
According to another feature of the invention, the rises, which are formed unitarily in the body by laser beam removal of material from a smooth-surfaced cylindrical blanlc, preferably in a wear-resistant ceramic coating of the blank are elongated generally circumferentially and have longitudinal extents or dimensions (axes) inclined at an arlgle c~ to the circumEerential direction of a maximum of10.
According to another aspect of the in~ention an apparatus for coating a web of paper or cardboard comprises:
two pressing rollers passing the web between them;
20~9 ~
1, ,~4 applicator means for applying to ~t least one of the rollers a flowable coating material; and along the one of the rollers downstTeam of the applicator means in a direction of rotation of the one of the rollers, a doctor bar for volumetric S metering of the flowable coating material onto one of the rollers and by the one of the rollers onto the web and comprising an elongated body formed with a generally cylindrical per;phery defLned by a surface distribution of discrete rises separated by troughs, the rises haYing outer faces lying along a cylindrical surface coaxial with 0 the body and being straight in a~al cross section, a total area of the faces constituting 10 % to 50 % of the area of the cylindrical penphery, and a profile depth Pt(2.5rnm) of the cylindrical periphery being between 30 ~m and 150~m according to German Industrial Standard DIN 4771.
Alternatively, the apparatus can comprise:
a counter roll around a portion of which the web is slung;
applicator means along this por~on for applying to the web a flowable coating material; and along the portion downstream of ~he applicator means in a direction of 20 rotation of the counter roll and in a direction of advance of the web, a doctor bar for volumetric metering of the flowable coating material onto the web and comprising an elongated body formed with a generally cylindrical peripheIy defined by a surface distribution of discrete Iises separated by troughs, the rises having outer faces lying along a ~lindrical surface coaxial with 5 the body and being straight in axial cro~s section, a total area of the faces constitu~ng 10 % to 50 ~ of the area of the cylindrical perip~ery, and ,:
, '4 2 ~ 2 ~ 8 9 ~
a profile depth Pt(2.5rmn~ of the cylindrical periphery being between 30 m and 150 ~m according to Gennan Industrial Standard DIN 4771.
Brief Description of the Drawing The above and other objects, features and advantages of my invention will 5 become more readily apparent from the following description, reference being made to the accompanying highly diagramrnatic drawing in which:
FIG. 1 is a partially broken away diagrarnmatically elevational view of a doctor bar according to the invention;
FlG. 2 is a diagrammatic section of one apparatus using the doctor bar of the 10 invention for coating a paper or cardboard web;
FlG. 3 is a view similar to ~IG. 2 of another apparatus for coating the paper or cardboard web;
FIG. 4 is a fragmentary section through a doctor bar of the invention drawn to a larger scale than FIG. l; and FIG. S is a partial elevational view of the doctor bar of FIG. 4, also drawn to a substantially larger scale than FIG. 1.
Specific Desc~ption The doctor bar illustrated in FIG. 1 comprises a generally cylindrical body 1 which originally was a smooth-surfilced cylinder and in which the entire periphery 20 has been subjected to a material-removal operation, e.g. a laser bearn machining operation, to form recesses 3 therein defining a multiplicity of generally elongated but otherwise randomly spaced rises 4 in an array extending over the entire sur~ace of the doctor bar. The faces of the rises 2 are smooth and in an axial cross section are flat, and lie in an imaginary surface of a cylinder C seen 25 in FIG. 4 as well, coaxial with the body, i.e. having the common axis A (FIG. 1) therewith.
17794 20~68~ 1 As can be seen from FIG. 4, the body 1 may be composed of a steel cylindrical rod 4 coated with a layer S of oxide ceramic which then has its cylindrical periphery polished. The grooves 3 are then forrned in the surface of the oxide ceramic in such manner that the coating material which is removed from the grooved 5 region is vaporized in a residue-free and burr-free manner. This provides an especially wear-resistant and smooth-surface array of rises.
Alternatively, bars with hardened and polished metal surfaces can be used in which the recesses are formed by means of diametric tools or by etching. Insteadof a material removal process the surface can be formed by a pressing operation or 10 embossing to form the rises or by applying material to the bar to constitute the rises which are then ground and polished to be sure that the faces of the rises lie in a common imaginary cylindrical surface.
The doctor bar shown in FIG. 1 can have a diarneter of 6rnm to 20mm and a length corlesponding to the working width of the coating device, i.e. possibly the lS full machine width, i.e. a length up to lOm.
The sum total oî the area of the faces of the rises, i.e. the area which is the coating of the web contacts ~he web or a transfer roller, preferably constitutes 10~o to 50% of the area of the imaginary cylindAcal surface. In terms of area, therefore, 50% to 90% of t~e original surface of the doctor bar will ~e20 removed. For a uniform and sufficiently high degree of coating, the surface is so machined that is has a profile depth Pt(2.5rnm) according to German Industrial Standard DIN 4771 which is between 3(~m and 15(~m as measured in $he axial direction of the doctor bar. Within this range there is only a slight variance in the profile depth. The deviation of individual profile depth measurements from the 25 main profile depth can amount to a maximum of S%.
A high degree of transfer to the coating material from the doctor blade to the web or trarlsfer roller can be achieved when the surface rouglmess Rt of thefla~ks of the recesses or rises is less t~ran 10% of the value of the Pt(2.Smm).
17~'`4 ~2~7 In that case there is little hangup of the coating liquid in the recesses between the rises.
Advantageously, as noted, the rises are elongated in outline and have their long dimensions extending generally circumferentially. Preferably the lengths L in 5 the circurnferential direction is ~etween lmm and 15mm while the width b of the rises in the axial direction is between 1(~m and 10(~m. In some ~ases, a rise can extend around the entire periphery. The spacing a of the rises 2 from one another preferably amounts to between 150~m and 40(~IIL
For a uniform coating it has been found to be advantageous to have the 10 geometric dimensions and dis~butions of the rises 2 generally randomly distributed wit'nin certain limits. The range of va~iations for the width ~2 measured in the axial direction can be between l(~m and 10~m while the range in variation for the spacing a can be between 15~m and 40(~rn.
For certain applications it has been found to be advantageous to orient the 15 elongated rises and an inclination to the longitudinal axis or the peripheraldirection. In the case shown in FIG. 1, for exarnple, the axes of ehe rises are inclined at angle ~ to the circumferential direction. The angle ~ can be a ma~num of 10 and may va~y randomly within the range of + 10.
For the coating of paper or cardboard with coloring materials, for e~ample, 20 it has been found to be advantageous to have the open cross section between rises in a central section of the bar on one side thereof equal to 15mm2 to 80mm2 per meter of the doctor bar length In FIG. 2 I ha~e shown an apparatus for applying glue or a colonng mat~rial to a paper or cardboard web 12 which is fed in the direction of arrow 13 wh~e 25 being slung around a coating drum 10. At an upstream portion of the path of the web, any conventional applicator 14, including a wiper l5 may be provided to transfer the coating liquid to the web so that t'ne web having the coating thereon is fed at 16 to the doctor bar 17. The la..er is received in an elastomeric holder 17794 ~2~;~97 18 on a rigid structure 19 (see German Patent 30 æ sss), for example, which illustrates a preferred mode of resiliently mounting the doctor bar.
The excess liquîd is removed by the doctor bar so that the coded product 20 has a uniform film of the coating agent.
In this embodiment, the doctor bar operates directly upon the paper or cardboard web to meter the c~ating material onto the latter and the roller 10 constitutes a counter roller which is underslung by the web and in the underslung region has the applicator and the doctor bar spaced apart one after the other in --~ - - - ~~ ~~~-~ -the web travel directiorL The doctor bar is elastically mounted. The apparatus of German Patent 30 22 955 can ~e used here, substituting the doctor bar of the invention for the smooth doctor bar of that patent.
In the system in which the glue or pigmented flowable material is applied indirectly to the web (FIG. 3) the coating device can comprise 2 placing rollers 30 and 36 through the nip of which the paper web 32 is based.
Along one or both of these rollers a nozzle or roller applicator can be provided as shown at 33 to deposit the coating material onto the transfer drum 30 as it is rotated in the direction of 31. A doctor bar 34 according to the invention ~corresponding to FIG. 1 or FI&S. 4 and 5) mounted in an elastic holder 17 to 19 as described, engages the drurn 30 to remove the excess coating liquid therefrorn. The doctor bar is driven in counter rotation to the press roller. A
coating device of this type is ~ound in DE-GM 84 14 413 and the preferred resilient support for the docto oar can be that fonnd nn German Patent 30 22 955.
~CIOR BAR FOR THE VOLUMETRIC I~TERING OF FLOWABLE
MATERL~LS ONI O A TRAVELLING WEB
SPECIFICATION
Fie~d of the ~nvention Our present invention relates to a doctor bar for the volumetric rnetering of coating materials, for example, glue or coloring fluids, onto travelling webs, for example, of paper or cardboard. The invention also relates to a coating apparatus using the improved doctor bar as a metering element for the coating material.
Background Qf thç LTIvention - -In the coating of travelling paper or cardboard webs, it is known to pro~ide a doctor bar having circumferential grooves defining on the bar, lands separated by the troughs defining the grooves. Such doctor bars are utilized for applying coloring or glue films to the surface of the web or for coating the web with pr~deterrnined quantities of the ~owable coating agent, the amount of which is ini~uenced by the groove cross section of the doctor bar.
The doctor bar can be applied directly to the web, if the coating material is applied thereto directly at an upstream location so that the doctor bar senes tocontrol the coating weight per ULUt area Alternatively, the doctor bar can function to control the quanti~ of the coating applied to a coating drum which tran~fe~ the coating liquid to the web. In that case, the doctor bar is provided downstream of the applicator in the direction of rotation of the transfer or coating roller or drum.
' 2 ~ 8 ~ 7 In that case, the doctor bar is provided downstream of the applicator in the direction of rotation of the transfer or coating roller or drurn.
In the case in which a roller or drum is underslung or overslung by the web, the applicator and metering doctor bar can be provided in succession in the path of S this roller or web. In the case of another coating system in which the web passes between rollers, one or both of the rollers can form transfer rollers as described and cooperate with applicators and doctor bars for controlling the flowable coating material applied to one or both of the rollers before the roller or rollers transfer the coating material to the web.
Doctor bars of conventional design are ~ound in such applications in German Open Application DE-OS 37 35 889 and in German Utility Model DE-GM 84 14 413. In~he first case, the doctor bar cooperates direct~y with the paper web whereas inthe second case the doctor bar serves to control the application of a film to a ~ansfer roller whicb, in the nip between two rollers, applies the coating material to the web.
It has been found that doctor bars in which the groove arrangement was formed by wrapping a wire around a cylindrical body, suffered from rapid wear. If eflorts are made to use rubber coated rollers in coniunction therewith, it is difficult to maintain constant conditions and there is a danger of darnage to the roller surface.
2û In German Patent Document DE-OS 38 41 494 a doctor bar is described which has a multiplicity of button-lL~ce protuberances along the surface. These can be fab-ricated by machining recesses in a cylindrical bar, by etching, milling, grinding, pressing, etc. The protuberances or the entire doctor bar can be composed of lowwearing materials, for example, hard materials such as titanium or tungsten, hard chromed steel, glass or oxide ceramic materials.
Notwithstandirlg the well developed character of this prior art, however, efforts to provide low wearing doctor bars capable of producing stripe-free thincoatings of coating liquids s,. the type descn~d on travelling webs, especiaiiy of ~2~8~7 paper or cardboard, have not been fully satisfactory. Furtherrnore, when the doctor bar was employed for applying coatings to ~ansfer rollers, damage to the transfer roller could not be excluded in many cases.
Objects of ~he Inventio~
It is, therefore, the principal object of the present invention to provide an improved doctor bar capable of stripe-free application of small-thickness coatings to travelling webs, especially of paper or cardboard, whereby the drawbacks of earlier systems are a~oided.
Yet another object of the invention is to provide a doctor bar which can be utilized effectively for the application of transferable coatings to a transfer roller without damage to the surface of this roller.
St;~l another object of the invention is to provide an improved apparatus for coating paper and cardboard webs having an irnproved doctor bar.
Summa~of the Invention These objects and others which will become apparent hereinafter are attained, in accordance with the invention in a doc~or bar for volumetric metering of a flowable coating material onto a web, especi~lly a paper or cardboard web, comprising an elongated body formed with a generally cylindrical periphery defined by a surface distribution of discrete rises separated by troughs, the rises having outer faces Iying along a cylindrical surface coaxial with the body and beirlg straight in alcial cross section;
a total area of the faces constituting 10 5'o to 50 % of the area of the cylindrical periphely; and a profile depth Pt(2.5mm) of the cylindrical periphery being between 30 ~ m and 150 ~m according i~ ~ennan Industrial Standard DIN 4771.
- l~q4 2~ 897 According to a feature of the invention each of the rises has flanks extending from the respective outer face to a ~loor of an adjacent trough, said flanks having a roughness depth Rt which is a maximum of 10 ~ of the profile depth Pt(2.5mm).
S Preferably the geometric dimensions and distributions of the rises varies along the cylindrical periphery randornly within predeterrnined limits.
According to a feature of the invention, the rises are generally elongated in a circumferential direction of the body, have widths b of substantially lO ~ m to lOO~m, and have spacings of substantially 1501sm to 400~m from one another.
The rises can have widths b randornly varying between substantially 10 ~ m and substantially 100 ~ m, and spacings randomly varying between substantially lSO~m to substantially 400~m from onç another.
The lengtbs of the rises extendin~ in the circurnferential direction can be between substantially lmm and lSmr~L
AdvaIltageously, the troughs defîne in a central longitudinal section through the doctor bar, an open cross sectional area between the rises on one side of the bar amounting to lS mm2 to 80 mm2 per meter of the length of the bar.
According to another feature of the invention, the rises, which are formed unitarily in the body by laser beam removal of material from a smooth-surfaced cylindrical blanlc, preferably in a wear-resistant ceramic coating of the blank are elongated generally circumferentially and have longitudinal extents or dimensions (axes) inclined at an arlgle c~ to the circumEerential direction of a maximum of10.
According to another aspect of the in~ention an apparatus for coating a web of paper or cardboard comprises:
two pressing rollers passing the web between them;
20~9 ~
1, ,~4 applicator means for applying to ~t least one of the rollers a flowable coating material; and along the one of the rollers downstTeam of the applicator means in a direction of rotation of the one of the rollers, a doctor bar for volumetric S metering of the flowable coating material onto one of the rollers and by the one of the rollers onto the web and comprising an elongated body formed with a generally cylindrical per;phery defLned by a surface distribution of discrete rises separated by troughs, the rises haYing outer faces lying along a cylindrical surface coaxial with 0 the body and being straight in a~al cross section, a total area of the faces constituting 10 % to 50 % of the area of the cylindrical penphery, and a profile depth Pt(2.5rnm) of the cylindrical periphery being between 30 ~m and 150~m according to German Industrial Standard DIN 4771.
Alternatively, the apparatus can comprise:
a counter roll around a portion of which the web is slung;
applicator means along this por~on for applying to the web a flowable coating material; and along the portion downstream of ~he applicator means in a direction of 20 rotation of the counter roll and in a direction of advance of the web, a doctor bar for volumetric metering of the flowable coating material onto the web and comprising an elongated body formed with a generally cylindrical peripheIy defined by a surface distribution of discrete Iises separated by troughs, the rises having outer faces lying along a ~lindrical surface coaxial with 5 the body and being straight in axial cro~s section, a total area of the faces constitu~ng 10 % to 50 ~ of the area of the cylindrical perip~ery, and ,:
, '4 2 ~ 2 ~ 8 9 ~
a profile depth Pt(2.5rmn~ of the cylindrical periphery being between 30 m and 150 ~m according to Gennan Industrial Standard DIN 4771.
Brief Description of the Drawing The above and other objects, features and advantages of my invention will 5 become more readily apparent from the following description, reference being made to the accompanying highly diagramrnatic drawing in which:
FIG. 1 is a partially broken away diagrarnmatically elevational view of a doctor bar according to the invention;
FlG. 2 is a diagrammatic section of one apparatus using the doctor bar of the 10 invention for coating a paper or cardboard web;
FlG. 3 is a view similar to ~IG. 2 of another apparatus for coating the paper or cardboard web;
FIG. 4 is a fragmentary section through a doctor bar of the invention drawn to a larger scale than FIG. l; and FIG. S is a partial elevational view of the doctor bar of FIG. 4, also drawn to a substantially larger scale than FIG. 1.
Specific Desc~ption The doctor bar illustrated in FIG. 1 comprises a generally cylindrical body 1 which originally was a smooth-surfilced cylinder and in which the entire periphery 20 has been subjected to a material-removal operation, e.g. a laser bearn machining operation, to form recesses 3 therein defining a multiplicity of generally elongated but otherwise randomly spaced rises 4 in an array extending over the entire sur~ace of the doctor bar. The faces of the rises 2 are smooth and in an axial cross section are flat, and lie in an imaginary surface of a cylinder C seen 25 in FIG. 4 as well, coaxial with the body, i.e. having the common axis A (FIG. 1) therewith.
17794 20~68~ 1 As can be seen from FIG. 4, the body 1 may be composed of a steel cylindrical rod 4 coated with a layer S of oxide ceramic which then has its cylindrical periphery polished. The grooves 3 are then forrned in the surface of the oxide ceramic in such manner that the coating material which is removed from the grooved 5 region is vaporized in a residue-free and burr-free manner. This provides an especially wear-resistant and smooth-surface array of rises.
Alternatively, bars with hardened and polished metal surfaces can be used in which the recesses are formed by means of diametric tools or by etching. Insteadof a material removal process the surface can be formed by a pressing operation or 10 embossing to form the rises or by applying material to the bar to constitute the rises which are then ground and polished to be sure that the faces of the rises lie in a common imaginary cylindrical surface.
The doctor bar shown in FIG. 1 can have a diarneter of 6rnm to 20mm and a length corlesponding to the working width of the coating device, i.e. possibly the lS full machine width, i.e. a length up to lOm.
The sum total oî the area of the faces of the rises, i.e. the area which is the coating of the web contacts ~he web or a transfer roller, preferably constitutes 10~o to 50% of the area of the imaginary cylindAcal surface. In terms of area, therefore, 50% to 90% of t~e original surface of the doctor bar will ~e20 removed. For a uniform and sufficiently high degree of coating, the surface is so machined that is has a profile depth Pt(2.5rnm) according to German Industrial Standard DIN 4771 which is between 3(~m and 15(~m as measured in $he axial direction of the doctor bar. Within this range there is only a slight variance in the profile depth. The deviation of individual profile depth measurements from the 25 main profile depth can amount to a maximum of S%.
A high degree of transfer to the coating material from the doctor blade to the web or trarlsfer roller can be achieved when the surface rouglmess Rt of thefla~ks of the recesses or rises is less t~ran 10% of the value of the Pt(2.Smm).
17~'`4 ~2~7 In that case there is little hangup of the coating liquid in the recesses between the rises.
Advantageously, as noted, the rises are elongated in outline and have their long dimensions extending generally circumferentially. Preferably the lengths L in 5 the circurnferential direction is ~etween lmm and 15mm while the width b of the rises in the axial direction is between 1(~m and 10(~m. In some ~ases, a rise can extend around the entire periphery. The spacing a of the rises 2 from one another preferably amounts to between 150~m and 40(~IIL
For a uniform coating it has been found to be advantageous to have the 10 geometric dimensions and dis~butions of the rises 2 generally randomly distributed wit'nin certain limits. The range of va~iations for the width ~2 measured in the axial direction can be between l(~m and 10~m while the range in variation for the spacing a can be between 15~m and 40(~rn.
For certain applications it has been found to be advantageous to orient the 15 elongated rises and an inclination to the longitudinal axis or the peripheraldirection. In the case shown in FIG. 1, for exarnple, the axes of ehe rises are inclined at angle ~ to the circumferential direction. The angle ~ can be a ma~num of 10 and may va~y randomly within the range of + 10.
For the coating of paper or cardboard with coloring materials, for e~ample, 20 it has been found to be advantageous to have the open cross section between rises in a central section of the bar on one side thereof equal to 15mm2 to 80mm2 per meter of the doctor bar length In FIG. 2 I ha~e shown an apparatus for applying glue or a colonng mat~rial to a paper or cardboard web 12 which is fed in the direction of arrow 13 wh~e 25 being slung around a coating drum 10. At an upstream portion of the path of the web, any conventional applicator 14, including a wiper l5 may be provided to transfer the coating liquid to the web so that t'ne web having the coating thereon is fed at 16 to the doctor bar 17. The la..er is received in an elastomeric holder 17794 ~2~;~97 18 on a rigid structure 19 (see German Patent 30 æ sss), for example, which illustrates a preferred mode of resiliently mounting the doctor bar.
The excess liquîd is removed by the doctor bar so that the coded product 20 has a uniform film of the coating agent.
In this embodiment, the doctor bar operates directly upon the paper or cardboard web to meter the c~ating material onto the latter and the roller 10 constitutes a counter roller which is underslung by the web and in the underslung region has the applicator and the doctor bar spaced apart one after the other in --~ - - - ~~ ~~~-~ -the web travel directiorL The doctor bar is elastically mounted. The apparatus of German Patent 30 22 955 can ~e used here, substituting the doctor bar of the invention for the smooth doctor bar of that patent.
In the system in which the glue or pigmented flowable material is applied indirectly to the web (FIG. 3) the coating device can comprise 2 placing rollers 30 and 36 through the nip of which the paper web 32 is based.
Along one or both of these rollers a nozzle or roller applicator can be provided as shown at 33 to deposit the coating material onto the transfer drum 30 as it is rotated in the direction of 31. A doctor bar 34 according to the invention ~corresponding to FIG. 1 or FI&S. 4 and 5) mounted in an elastic holder 17 to 19 as described, engages the drurn 30 to remove the excess coating liquid therefrorn. The doctor bar is driven in counter rotation to the press roller. A
coating device of this type is ~ound in DE-GM 84 14 413 and the preferred resilient support for the docto oar can be that fonnd nn German Patent 30 22 955.
Claims (20)
1. A doctor bar for volumetric metering of a flowable coating material onto a web, especially a paper or cardboard web, comprising an elongated body formed with a generally cylindrical periphery defined by a surface distribution of discrete rises separated by troughs, said rises having outer faces lying along a cylindrical surface coaxial with said body and being straight in axial cross section;
a total area of said faces constituting 10 % to 50 % of the area of said cylindrical periphery; and a profile depth Pt(2.5mm) of said cylindrical periphery being between 30 µm and 150µm according to German Industrial Standard DIN 4771.
a total area of said faces constituting 10 % to 50 % of the area of said cylindrical periphery; and a profile depth Pt(2.5mm) of said cylindrical periphery being between 30 µm and 150µm according to German Industrial Standard DIN 4771.
2. The doctor bar defined in claim 1 wherein each of said rises has flanks extending from the respective outer face to a floor of an adjacent trough, said flanks having a roughness depth Rt which is a maximum of 10 % of said profile depth Pt(2.5mm).
3. The doctor bar defined in claim 1 wherein the geometric dimensions and distribution of said rises varies along said cylindrical periphery randomly within predetermined limits.
4. The doctor bar defined in claim 1 wherein said rises are generally elongated in a circumferential direction of said body, have widths b of substantially 10µm to 100µm, and have spacings of substantially 150 µm to 400µm from one another.
1779?
1779?
5. The doctor bar defined in claim 1 wherein said rises have widths b randomly varying between substantially 10µm and substantially 100µm and spacings randomly varying between substantially 150µm to substantially 400 µm from one another.
6. The doctor bar defined in claim 1 wherein said rises have lengths extending generally circumferentially of said body between substantially 1 mm and 15mm.
7. The doctor bar defined in claim 1 wherein said troughs define in a central longitudinal section through said doctor bar, an open cross sectional area between the rises on one side of the bar amounting to 15mm2 to 80mm2 per meter of the length of said bar.
8. The doctor bar defined in claim 1 wherein said rises are elongated generally circumferentially and have longitudinal extents inclined at an angle .alpha. to the circumferential direction of a maximum of 10°.
9. The doctor bar defined in claim 1 wherein said rises are formed unitarily in said body by removal of material from a smooth-surfaced cylindrical blank.
10. The doctor bar defined in claim 9 wherein said rises are formed in a wear-resistant coating of said blank.
11. The doctor bar defined in claim 10 wherein said wear-resistant coating of said blank is a ceramic and said rises are formed by laser machining of said troughs in said ceramic.
12. An apparatus for coating a web of paper or cardboard, said apparatus comprising:
two pressing rollers passing said web between them;
applicator means for applying to at least one of said rollers a flowable coating material; and along said one of said rollers downstream of said applicator means in a direction of rotation of said one of said rollers, a doctor bar for volumetric metering of said flowable coating material onto one of said rollers and by said one of said rollers onto said web and comprising an elongated body formed with a generally cylindrical periphery defined by a surface distribution of discrete rises separated by troughs, said rises having outer faces lying along a cylindrical surface coaxial with said body and being straight in axial cross section, a total area of said faces constituting 10 % to 50 % of the area of said cylindrical periphery, and a profile depth Pt(2.5mm) of said cylindrical periphery being between 30 µm and 150µm according to German Industrial Standard DIN 4771.
two pressing rollers passing said web between them;
applicator means for applying to at least one of said rollers a flowable coating material; and along said one of said rollers downstream of said applicator means in a direction of rotation of said one of said rollers, a doctor bar for volumetric metering of said flowable coating material onto one of said rollers and by said one of said rollers onto said web and comprising an elongated body formed with a generally cylindrical periphery defined by a surface distribution of discrete rises separated by troughs, said rises having outer faces lying along a cylindrical surface coaxial with said body and being straight in axial cross section, a total area of said faces constituting 10 % to 50 % of the area of said cylindrical periphery, and a profile depth Pt(2.5mm) of said cylindrical periphery being between 30 µm and 150µm according to German Industrial Standard DIN 4771.
13. The apparatus defined in claim 12 wherein each of said rises has flanks extending from the respective outer face to a floor of an adjacent trough, said flanks having a roughness depth Rt which is a maximum of 10 % of said profile depth Pt(2.5mm).
14. The apparatus defined in claim 13 wherein the geometric dimensions and distribution of said rises varies along said cylindrical periphery randomly within predetermined limits.
15. The apparatus defined in claim 14 wherein said rises are generally elongated in a circumferential direction of said body, have widths b of substantially 10µm to 100µm, and have spacings of substantially 150 µm to 400µm from one another.
16. An apparatus for coating a web of paper or cardboard, said apparatus comprising:
a counter roll around a portion of which said web is slung;
applicator means along said portion for applying to said web a flowable coating material; and along said portion downstream of said applicator means in a direction of rotation of said counter roll and in a direction of advance of said web, a doctor bar for volumetric metering of said flowable coating material onto said web and comprising an elongated body formed with a generally cylindrical periphery defined by a surface distribution of discrete rises separated by troughs, said rises having outer faces lying along a cylindrical surface coaxial with said body and being straight in axial cross section, a total area of said faces constituting 10 % to 50 % of the area of said cylindrical periphery, and a profile depth Pt(2.5mm) of said cylindrical periphery being between 30 µm and 150µm according to German Industrial Standard DIN 4771.
a counter roll around a portion of which said web is slung;
applicator means along said portion for applying to said web a flowable coating material; and along said portion downstream of said applicator means in a direction of rotation of said counter roll and in a direction of advance of said web, a doctor bar for volumetric metering of said flowable coating material onto said web and comprising an elongated body formed with a generally cylindrical periphery defined by a surface distribution of discrete rises separated by troughs, said rises having outer faces lying along a cylindrical surface coaxial with said body and being straight in axial cross section, a total area of said faces constituting 10 % to 50 % of the area of said cylindrical periphery, and a profile depth Pt(2.5mm) of said cylindrical periphery being between 30 µm and 150µm according to German Industrial Standard DIN 4771.
17. The apparatus defined in claim 16 wherein said rises have widths b randomly varying between substantially 10µm and substantially 100 µm, and spacings randomly varying between substantially 150µm to substantially 400 µm from one another.
18. The apparatus defined in claim 17 wherein said rises have lengths extending generally circumferentially of said body between substantially 1 mm and 15mm.
19. The apparatus defined in claim 18 wherein said troughs define in a central longitudinal section through said doctor bar, an open cross sectional area between the rises on one side of the bar amounting to 15mm2 to 80mm2 per meter of the length of said bar
20. The apparatus defined in claim 19 wherein said rises are elongated generally circumferentially and have longitudinal extents inclined at an angle to the circumferential direction of a maximum of 10°.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE19893937749 DE3937749A1 (en) | 1989-11-14 | 1989-11-14 | Squeegee rod for volumetric dosing of coating material |
| DEP3937749.0 | 1989-11-14 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA2026897A1 true CA2026897A1 (en) | 1991-05-15 |
Family
ID=6393443
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA 2026897 Abandoned CA2026897A1 (en) | 1989-11-14 | 1990-10-04 | Doctor bar for the volumetric metering of flowable materials onto a travelling web |
Country Status (6)
| Country | Link |
|---|---|
| EP (1) | EP0427924A3 (en) |
| JP (1) | JPH03178366A (en) |
| BR (1) | BR9005436A (en) |
| CA (1) | CA2026897A1 (en) |
| DE (1) | DE3937749A1 (en) |
| FI (1) | FI905624A0 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101489799B (en) * | 2006-07-19 | 2012-09-26 | 费利克斯伯切尔有限及两合公司 | Stochastically lasered film roller |
Families Citing this family (10)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| DE4123326C2 (en) * | 1991-07-15 | 1994-11-17 | Horst Sprenger Gmbh | Doctor blade shaft for coating and coating systems as well as for glue and film presses |
| FI93885C (en) * | 1992-05-21 | 1995-06-12 | Valmet Paper Machinery Inc | Coating device for coating a roll of glue press, paper or board |
| DE4317657C1 (en) * | 1993-05-27 | 1994-07-14 | Voith Gmbh J M | Coating device for coating running webs |
| US5599393A (en) * | 1995-04-25 | 1997-02-04 | Macmillan Bloedel Limited | Metering rod coaters |
| DE19840951A1 (en) * | 1998-09-08 | 2000-03-09 | Jagenberg Papiertech Gmbh | Doctor rod for a coating device |
| JP2002239431A (en) * | 2001-02-13 | 2002-08-27 | Mitsubishi Heavy Ind Ltd | Coating apparatus and method for manufacturing coated paper |
| JP4460257B2 (en) | 2003-10-02 | 2010-05-12 | 富士フイルム株式会社 | Coating rod and manufacturing method thereof |
| JP5175149B2 (en) * | 2007-09-14 | 2013-04-03 | 日本製紙株式会社 | Manufacturing method of coated paper |
| DE102009026495A1 (en) * | 2009-05-27 | 2010-12-02 | Voith Patent Gmbh | doctor device |
| GB2533313A (en) * | 2014-12-15 | 2016-06-22 | Airbus Operations Ltd | Flowable material applicator |
Family Cites Families (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB729561A (en) * | 1952-05-19 | 1955-05-11 | Strachan & Henshaw Ltd | Improvements in or relating to inking rolls of rotary printing presses |
| BE678130A (en) * | 1965-04-08 | 1966-09-21 | ||
| GB1486142A (en) * | 1975-03-10 | 1977-09-21 | Wiggins Teape Ltd | Coating apparatus |
| DE3033478C2 (en) * | 1980-09-05 | 1982-12-30 | Fa. Johannes Zimmer, 9020 Klagenfurt | Foulard with a wrap-around roller for a textile web to be treated |
| JPS6089827A (en) * | 1983-10-22 | 1985-05-20 | Konishiroku Photo Ind Co Ltd | Method and apparatus of flat coating film |
| US4664058A (en) * | 1985-10-25 | 1987-05-12 | International Paper Company | Coating roll surface configuration for applying liquid sterilant to a moving web |
| DE3703834A1 (en) * | 1987-02-07 | 1988-08-18 | Jagenberg Ag | ROLLER SCRAPER APPLICATION TO APPLY COATINGS ON MATERIALS |
-
1989
- 1989-11-14 DE DE19893937749 patent/DE3937749A1/en not_active Withdrawn
-
1990
- 1990-08-09 EP EP19900115282 patent/EP0427924A3/en not_active Withdrawn
- 1990-10-04 CA CA 2026897 patent/CA2026897A1/en not_active Abandoned
- 1990-10-26 BR BR9005436A patent/BR9005436A/en unknown
- 1990-11-09 JP JP30280390A patent/JPH03178366A/en active Pending
- 1990-11-13 FI FI905624A patent/FI905624A0/en not_active Application Discontinuation
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101489799B (en) * | 2006-07-19 | 2012-09-26 | 费利克斯伯切尔有限及两合公司 | Stochastically lasered film roller |
| US8561536B2 (en) | 2006-07-19 | 2013-10-22 | Felix Boettcher Gmbh & Co. Kg | Stochastically lasered film roller |
| TWI461306B (en) * | 2006-07-19 | 2014-11-21 | Boettcher Gmbh & Co Felix | Stochastically laser-treated film roller |
Also Published As
| Publication number | Publication date |
|---|---|
| DE3937749A1 (en) | 1991-05-16 |
| EP0427924A3 (en) | 1991-11-13 |
| BR9005436A (en) | 1991-09-17 |
| FI905624A0 (en) | 1990-11-13 |
| JPH03178366A (en) | 1991-08-02 |
| EP0427924A2 (en) | 1991-05-22 |
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