CA1054873A - Coating method and apparatus therefor - Google Patents
Coating method and apparatus thereforInfo
- Publication number
- CA1054873A CA1054873A CA219,332A CA219332A CA1054873A CA 1054873 A CA1054873 A CA 1054873A CA 219332 A CA219332 A CA 219332A CA 1054873 A CA1054873 A CA 1054873A
- Authority
- CA
- Canada
- Prior art keywords
- coating
- web
- members
- coating member
- nip
- 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.)
- Expired
Links
Classifications
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
- B05D1/00—Processes for applying liquids or other fluent materials
- B05D1/26—Processes for applying liquids or other fluent materials performed by applying the liquid or other fluent material from an outlet device in contact with, or almost in contact with, the surface
-
- 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
- B05C5/00—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work
- B05C5/02—Apparatus in which liquid or other fluent material is projected, poured or allowed to flow on to the surface of the work the liquid or other fluent material being discharged through an outlet orifice by pressure, e.g. from an outlet device in contact or almost in contact, with the work
- B05C5/0254—Coating heads with slot-shaped outlet
- B05C5/0266—Coating heads with slot-shaped outlet adjustable in length, e.g. for coating webs of different width
-
- 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
- B05C9/00—Apparatus or plant for applying liquid or other fluent material to surfaces by means not covered by any preceding group, or in which the means of applying the liquid or other fluent material is not important
- B05C9/04—Apparatus or plant for applying liquid or other fluent material to surfaces by means not covered by any preceding group, or in which the means of applying the liquid or other fluent material is not important for applying liquid or other fluent material to opposite sides of the work
Landscapes
- Coating Apparatus (AREA)
- Application Of Or Painting With Fluid Materials (AREA)
Abstract
ABSTRACT OF THE DISCLOSURE
Method and apparatus for substantially simultaneously coating both surfaces of a web of indeterminate length. The web is fed in an upward direction and passes between a pair of coating members. The coating ?mposition is dispensed from an elongated slot and each coating member arranged transverse to the direction of movement of the paper web. An excess amount of coating composition is dispensed so as to form a dam at the nip defined by the confronting surfaces of the web and the spreading surface or lip of each coating member to assure uniform coating of the surface. The hydraulic pressure provided by the liquid composition passing between the spreading surface of the coating member and the web contributes to the stability of the web and hence attenuates any fluttering of the web.
The spreading surfaces of the coating members are arranged in a staggered position relative to the direction of movement of the web and preferably arranged to overlap one another so as to cause the path of the web in the region of the coating members to deviate from an imaginary straight line and hence to be pulled somewhat over each spreading surface which advantageously compensates for any irregulari-ties in the spreading surfaces.
The orientation of the coating members and the dispensing outlets, as well as the rate at which coating composition is dispensed are all made independently adjustable to enhance regulation of the thickness and uniformity of the coating layers deposited upon the web.
Method and apparatus for substantially simultaneously coating both surfaces of a web of indeterminate length. The web is fed in an upward direction and passes between a pair of coating members. The coating ?mposition is dispensed from an elongated slot and each coating member arranged transverse to the direction of movement of the paper web. An excess amount of coating composition is dispensed so as to form a dam at the nip defined by the confronting surfaces of the web and the spreading surface or lip of each coating member to assure uniform coating of the surface. The hydraulic pressure provided by the liquid composition passing between the spreading surface of the coating member and the web contributes to the stability of the web and hence attenuates any fluttering of the web.
The spreading surfaces of the coating members are arranged in a staggered position relative to the direction of movement of the web and preferably arranged to overlap one another so as to cause the path of the web in the region of the coating members to deviate from an imaginary straight line and hence to be pulled somewhat over each spreading surface which advantageously compensates for any irregulari-ties in the spreading surfaces.
The orientation of the coating members and the dispensing outlets, as well as the rate at which coating composition is dispensed are all made independently adjustable to enhance regulation of the thickness and uniformity of the coating layers deposited upon the web.
Description
~054873 FIELD OF THE INVENTION
The present invention relates to a coating method and apparatus and more particularly to a novel method and apparatus for substantially simulta-neously coating both sides of a web in a controlled uniform manner.
BACKGROUND OF THE INVENTION
There exists a variety of applications in which it is desired to coat both surfaces of a web. In one existing technique, the web is moved substantially vertically upward so as to pass between a pair of opposing coating members for applying a coating composition upon the paper web. The coating members are rigid and are positioned with respect to the web so as to provide a gap between the associated surface of the web and the respective coating member to cause a dam of coating composition to be formed in the nip between each surface of the web and the associated displaced surfaces of the coating members. The hydraulic pressure created by the movement of the web and the coating composition, in passing each coating member, serves to stabilize the web and prevent any fluttering or vibration of the web as it moves between the coating members. The web is coated with an excess of coating composition which is uniformly spread and scraped from each surface of the web in a subsequent operation by means of an opposing pair of flexible doctors typically comprising a pair of thin steel blades arranged in align-ment with one another and on opposite sides of the web whereby the excess coating composition removed from the web is returned to the system. Typi-cally the excess coating composition is admixed with fresh coating composition before reuse.
Careful observation of the aforementioned apparatus has shown that the distance between the rigid coating members is of considerable importance.
This distance must be adjusted with respect to both the thickness of the web and the quantity of coating composition applied upon the surfaces of the web so that the desired excess is deposited upon the web. These adjustments have, in turn, led to a number of complications. For example, if the excess quantity of coating composition is to be kept low at the primary coating location, the opposed rigid coating members must be set relatively close to - 3 - 'n~
~054873 one another. Since the coating members are rigid to prevent any instability in the web during the coating composition, thicker sections of the web which may be due to the presence of lumps or other impurities, may become lodged in the passageway between the opposed rigid coating members thus causing a fracture or tearing of the web.
Furthermore, the techniques employed in manufacturing the rigid coating members must be quite precise in order to produce rigid coating members having sufficiently straight and flat surfaces along the portions of the coating members which control the spreading of the excess coating com-position. If for example the coating members have a length of the order of 3 meters or more measured in the direction transverse to the direction of movement of the web this leads to serious problems. Even assuming that such precise manufacturing techniques are employed, it has also been found that temperature variations in the coating composition being dispensed can cause deviations (i.e., "warping") in the straight flat surfaces of the coating members. Such deviations in the contacting surfaces may cause portions of the web to remain uncoated since the dam formed in the nip between the web and the coating member may temporarily disappear due to the warping, especially if a relatively small excess quantity of coating com-position is applied.
BRIEF DESCRIPTION OF THE INVENTION AND OBJECTS
A primary object of the present invention is to provide method and apparatus which eliminates the above-mentioned disadvantages through the utilization of a technique which applies the coating composition on each surface of the web through outlets having orifices along the contact sur-faces of the coating members facing the web and by arranging the aforesaid contact surfaces in a spaced fashion in the direction of the movement of the web.
Thus, according to the present invention, instead of using the arrangement of the prior art in which the opposed coating members are located directly opposite one another, the present invention proposes an arrangement whereby the coating members are displaced with respect to one another relative to the direction of travel of the web, which arrangement consider-ably reduces the need for making the contacting surfaces of the coating members absolutely straight which further serves to reduce the otherwise stringent manufacturing requirements necessary to produce the coating members of the prior art.
In accordance with one embodiment of the subject invention, the supply of the coating agent as well as the positioning of the appropriate contacting surfaces in relation to the ass~ociated surface of the web are set so that an excess dam of coating composition is formed immediately before the nip between the contact surface of each coa~ing member and the associated surface of the web. It has been found that the hydraulic pressure created by the movement of the web and the coating composition deposited thereon serves to stabilize the web so that it floats or is suspended between the opposed layers of coating compositions which acts much like a lubricant in that it facilitates the smooth and stabilized passage of the web between the rigid coating members.
The coating result is further improved if the initial direction of travel of the web i5 altered as the web passes each of the rigid coating members which is accomplished by lateral displacement of the surfaces of the coating members contacting the web, said lateral displacement being transverse to the normal direction of travel of the web. It has been found that this deflection of the web further enhances stabilization of the web which is an important factor when the means proposed according to the present invention is employed as a primary coating station positioned to the upstream side of a pair of opposed flexible doctors which function to spread the coating composition in a uniform manner and scrape off any excess. It is important that the web be stabilized prior to its passage between the flexible doctor since vibrations or the like due to the instability or fluttering of the web passing through the primary coating station will cause the flexible doctors to be deflected from their desired position leading to a non-uniform and hence unacceptable coating layer.
In accordance with another embodiment of the present invention, the entire coating process can be effectively controlled by means of an adjust-able displacement of the coating composition dispensing members after the coating members have been properly positioned against the web.
As has been mentioned hereinabove, it is necessary to form a dam of the coating in order to assure a uniform coating layer devoiding uncoated spots. This is for example accomplished through the utilization of rotatable contact members having elongated dispensing slots whereby the members are adjustable to set the dispensing slots at a suitable angle relative to the web so that the desired quantity of coating composition is supplied to the web and a suitable quantity of coating composition will be dispensed to form the dam with a certain excess amount thereof possibly dripping downwardly from the region of the dam. This complete control of the coating process is thus obtained by adjusting the quantity of coating composition supplied and by aligning the dispensing slots at a suitable angle relative to the web.
The present invention also contemplates means for performing the method described hereinabove through the employment of outlet orifices for the coating composition which are located within the contact surfaces of the coating members positioned against each surface of the web and by staggering the contact surfaces relative to the path of movement of the web.
The present invention is further characterized in that the contact surface of one coating member may be positioned above the opposing contact surface of the other coating member to be arranged in an overlapping fashion thereby causing the path of movement of the web to be altered as it passes each contact surface so that the web moves in an undulating or "zig-zag"
fashion as it passes through the primary coating station.
The contact surfaces of each coating member may be shaped in the form of a pair of lips which taper in the direction of the paper web with the lips surrounding and hence defining the supply channel and outlet orifice for the coating composition.
According to another preferred embodiment of the invention, the contact surfaces of the coating members may comprise tubular members extending substantially across the entire width of the web whereby each tubular member includes an elongated slot-like outlet opening for dispensing a coating agent, which opening extends substantially across the entire width of the web. The tubular members are preferably pivotably journalled and so arranged as to permit adjustable orientation of the outlet slots, which adjustments are independent of the rotatably adjustable contact members.
In the case where it is desired to provide an uncoated marginal portion along each edge of the web, adjustable screening strips may be arranged within the slot-like openings so as to be adjustable displaceable within the slot at the opposing ends thereof.
In order to avoid non-uniform coating of the web due to a pressure drop in the coating agent as it moves toward the outlet slots, the distri-bution chambers for the coating agent are preferably connected by means of a plurality of supply conduits distributed at spaced intervals along the length of the coating members and communicating with an inner chamber located in the lower portion of each coating member, which inner chamber preferably has a greater storage volume than the distribution chamber. The supply conduits may preferably be comprised of flexible plastic tubes or the like.
In order to prevent the coating members from becoming clogged or dirty, the portions of the coating members which comprise the contact sur-faces may be rotatably journalled in holders having intermediate seals. An upper covering plate may also be arranged above each contact surface portion to protect the contact surface portions from excess coating composition which may drip downwardly from upper portions of the web as it leaves the primary coating station.
BRIEF DESCRIPTION OF THE FIGURES
The above as well as other objects of the invention will become apparent when reading the accompanying description and drawings in which:
Figure 1 shows a sectional elevational view of a first embodiment of a coating means designed in accordance with the principles of the present invention;
Figure 2 shows an elevational sectional view of a second preferred embodiment of the present invention;
Figure 3 shows an enlarged detailed view of a portion of one coating member of Figure 2;
Figure 4 is a sectional elevational view of still a third embodiment of the present invention;
Figure 5 shows an enlarged detailed view of a portion of one coating member of Figure 4;
Figure 6 shows a perspective view of a tubular dispensing member of the type shown in Figures 2 - 5 and employing a screening element;
Figure 7 is a perspective view showing the screening element and tubular member of Figure 6 in greater detail; and Figure 8 is a sectional view showing one technique for pivotally mounting the supply container of Figure 2 and 4, for example.
DETAILED DESCRIPTION OF THE INVENTION
The embodiment of Figure 1 shows a paper web 1 which is conveyed in the upward vertical direction shown by arrow A. Although not shown for purposes of simplicity, the movement of the paper web is typically con-trolled by dispensing the untreated paper web from a supply reel typically positioned beneath the apparatus of Figure 1 and winding the subsequently treated paper web upon a wind-up reel typically positioned above the apparatus of Figure 1. The system may further include other guiding rollers, drying members, and the like, which have also been omitted for purposes of simpli-city.
The upwardly moving web passes between coating members 2 and 3 positioned on opposite sides of the paper web. The coating members 2 and 3 are pivotally journalled about longitudinal axes 4a and 5a, for example, by elongated shafts 4 and 5, whose free ends may be journalled within suitable bearings (not shown). The coating members may be rotated to accurately position their respective contact surfaces 6 and 7 by means of coarse and fine adjustment assemblies.
The coating members 2 and 3 are each respectively provided with a hollow interior chamber 8 and 9 containing the coating composition supplied thereto through suitable conduits, not shown. Each of the chambers 8 and 9 is respectively provided with an outfeed channel 10 and 11 communicating with the chambers 8 and 9 and with the contact surfaces 6 and 7 whereby the channels 10 and 11 terminate in the elongated slot-like outlets 12 and 13 positioned between the pairs of lips 14 - 15 and 16 - 17. The contact surfaces of the lips are arranged somewhat obliquely relative to the direction of movement of paper web 1.
The coating members 2 and 3 are preferably set with respect to one another so that the outlets 12 and 13 and the pairs of lips 14 - 15 and 16 - 17 are arranged in staggered fashion relative to the path of movement of the paper web and further so that the contact surfaces overlap one another slightly, i.e. so that they are displaced somewhat relative to the otherwise straight line path of movement of the paper web. Due to this displacement, paper web 1 will be slightly deflected or curved as it passes the contact surfaces 6 and 7.
The coating agent dispensed through the outlet openings 12 and 13 is supplied at a rate sufficient to cause dams 20 and 21 to form between each surface of the paper web and the associated contact surface 6 and 7 of the coating members 2 and 3. Coating composition in excess of that necessary to form the dam runs downwardly under the influence of gravity along the surfaces 18 and 19. The hydraulic pressure created by the excess coating composition contributes to stabilization of the paper web as it passes between coating members 2 and 3 causing the web to float or be suspended between the layers of coating composition which acts in much the same way as a lubrica-ting agent. The formation of the dams further prevents the occurrence of a non-uniform coating caused by formation of air bubbles in the coating compo-sition.
It can readily be understood that the arrangement of the coating members of Figure 1 considerably reduces the requirements that the contact surfaces 6 and 7 be perfectly straight due to the fact that the paper web is somewhat pulled around each contact surface enabling the web to compensate for any uneveness in the straightness of the contact members so that any deviation from the straight flat contact surfaces will not affect the result _ g _ ~054873 of the coating process.
Figure 2 shows another preferred embodiment of the present in~ention in which the contact surfaces 6 and 7 of the embodiment of Figure 1 are replaced by elongated tubular members 22 and 23 which extend along the entire width of paper web 1 and are preferably pivotably journalled in a holder substantially comprised of plates 18 - 24 and 19 - 25 which define the inner and outer sides of coating members 2 and 3. As can best be seen from Figure 3, the above-mentioned plates pivotally hold the tubular members, such as, for example, the tubular member 22 with the aid of brackets 26a and 27a and intermediate seals 26 and 27 preferably secured to the inner surfaces of plates 18 and 24 by clamping brackets 26a and 27a. Each of the tubular members are respectively provided with interior distributing chambers 28 and 29 for receiving the coating compound. Each distributing chamber is in communication with the larger chambers 40 and 41 defined by hollow elongated tubular members 38 and 39, respectively, by means of flexible tubular supply conduits 30 arranged at spaced intervals along the length of each of the members 22 and 23 (note, for example, Figure 7). Each of the tubular members 30, which may preferably be formed of a transparent resilient plastic material, is force-fitted over connection nipples 31 in members 38 and 39 and connection nipples 32 in members 22 and 23.
Tubular members 22 and 23 are each provided with elongated slot-like outlet openings 33 and 34 extending over the entire length of members 22 and 23 and directed toward an associated surface of the paper web.
Tubular members 22 and 23 are preferably pivotable about their longitudinal axes 22a and 23a to such an extent that the position of each outlet can be altered to position slot 33, for example, (see Figure 3) an angular distance a above the solid line position 33 or, alternatively, an angular distance b below solid line position 33. It should further be noted that the tubular members 22 and 23 may be rotated independently of the coating members 2, 3 about their axes of rotation designated by numerals 22a and 23a in Figure 2.
The distance X, shown in Figure 2, represents one suitable vertical displacement between the contact surfaces of the tubular members 22 and 23 measured in the direction of travel of paper web 1.
The arrangement of Figure 2 has the advantage, inter alia, since the tubular members 22 and 23 are rotatably mounted to enable these members to be turnable to some extent independently of each other due to the fact that they are connected to associated members 38 and 39 by flexible tubes 30. The ends of each of the coating members 38 and 39 may be mounted in rotatable seals as shown in Figure 8. End 38a, for example, has a reduced diameter portion 38a encompassed by rotatable seal 50 provided in sidewall 51. The opposite end 38b of member 38 is closed and is pivotally mounted within the opening 52a in side wall 52. If desired, a bearing may be provided between opening 52a and the reduced diameter portion of end 38b. Conduit 53 is coupled to a suitable supply of coating composition.
If desired, the ends of tubular members 22 and 23 may be configured in the manner of end 38b of member 38 so as to be received in openings in side-walls 51 and 52, to further facilitate the ability of members 22 and 23 to revolve, whereby the coating process is entirely under control when in operation. For example, the quantity of coating agent which drips down-wardly along the exterior surfaces of plates 18 and 19 and the quantity of coating agent supplied to the paper web, as well as the formation of dams 20 and 21 of a suitable size, can be set so as to create each dam immediately adjacent the nip formed by the paper web and the portion of the contact surface engaging the web. Another advantage of the arrangement shown in Figure 2 resides in the fact that tubular members 22 and 23 are inexpensive in that they can be manufactured rather simply and hence cheaply. Alter-natively, the tubes need not be perfect cylinders but may, for example, be truncated cylinders having their curved surface portions engaging web 1.
Members having other suitable cross-sectional configurations may also be used in place of tubular members, if desired. In addition, the configuration of the outlet slots may be altered from that shown in Figure 2.
For example, the contact surfaces may consist of lips protruding outwardly from the arcuate surface members 22 and 23 and being spaced from one another so as to define the outlet opening therebetween.
1~54873 Figure 4 shows still another embodiment of the present invention which, while substantially similar to the embodiment of Figure 2, shows the covering plates 24 and 25 as having upwardly extending portions 24a and 25a to enclose a substantial portion of the tubular members 22 and 23 and thereby protect the tubular members from collecting dirt or coating composition which may drip down from above.
Figure 5 shows a more detailed view of the upper portion of coating member 2 in which the seals 26 and 27 of Figure 2 are replaced by scrapers 26' and 27' formed of rubber or flexible steel clamped to the inner surfaces of plate portions 18 and 18a by clamping brackets 18b and 18c. The flexible scrapers prevent coating compound from entering into the hollow interior of coating members 2 and 3.
Figures 6 and 7 show the manner in which coating dispensing slot 33 provided in tubular member 22 may be at least partially sealed or screened off by means of a screening strip 35 which is inserted into slot 33 so as to completely fill lengthwise portion L of slot 33. It should be understood that a similar screening strip may be adjustably positioned within the opposite end of slot 33. Figure 7 shows screening strip 35 inserted into slot 33 so that a marginal portion M of the paper web 1 is maintained free of the coating agent. Obviously, the width of the uncoated marginal portion M may be adjusted by suitable adjustment of the screening strips.
It can be seen from the foregoing description that the present invention provides a novel method and apparatus for substantially simultan-eously coating both sides of a web by means of independently adjustable staggered overlapping contact members which assure uniform distribution of the coating composition over each surface of the web while compensating for any unevenness in the contact members due to the novel zig-zag manner in which the web moves in passing through the coating station by making the contact surfaces and coating composition dispensing slot independently adjustable. Location of the dam of coating can be suitably adjusted so as to be positioned immediately adjacent the nip formed between the web and ~054873 the associated contact surface.
Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. For example, as was mentioned hereinabove, the coating apparatus can also be used as a primary coating station in con-junction with a secondary scraping station positioned above the primary coating station and comprising two opposed flexible doctors. Also, the means proposed according to the present invention can be utilized to coat opposite sides of the web with different coating compounds. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.
The present invention relates to a coating method and apparatus and more particularly to a novel method and apparatus for substantially simulta-neously coating both sides of a web in a controlled uniform manner.
BACKGROUND OF THE INVENTION
There exists a variety of applications in which it is desired to coat both surfaces of a web. In one existing technique, the web is moved substantially vertically upward so as to pass between a pair of opposing coating members for applying a coating composition upon the paper web. The coating members are rigid and are positioned with respect to the web so as to provide a gap between the associated surface of the web and the respective coating member to cause a dam of coating composition to be formed in the nip between each surface of the web and the associated displaced surfaces of the coating members. The hydraulic pressure created by the movement of the web and the coating composition, in passing each coating member, serves to stabilize the web and prevent any fluttering or vibration of the web as it moves between the coating members. The web is coated with an excess of coating composition which is uniformly spread and scraped from each surface of the web in a subsequent operation by means of an opposing pair of flexible doctors typically comprising a pair of thin steel blades arranged in align-ment with one another and on opposite sides of the web whereby the excess coating composition removed from the web is returned to the system. Typi-cally the excess coating composition is admixed with fresh coating composition before reuse.
Careful observation of the aforementioned apparatus has shown that the distance between the rigid coating members is of considerable importance.
This distance must be adjusted with respect to both the thickness of the web and the quantity of coating composition applied upon the surfaces of the web so that the desired excess is deposited upon the web. These adjustments have, in turn, led to a number of complications. For example, if the excess quantity of coating composition is to be kept low at the primary coating location, the opposed rigid coating members must be set relatively close to - 3 - 'n~
~054873 one another. Since the coating members are rigid to prevent any instability in the web during the coating composition, thicker sections of the web which may be due to the presence of lumps or other impurities, may become lodged in the passageway between the opposed rigid coating members thus causing a fracture or tearing of the web.
Furthermore, the techniques employed in manufacturing the rigid coating members must be quite precise in order to produce rigid coating members having sufficiently straight and flat surfaces along the portions of the coating members which control the spreading of the excess coating com-position. If for example the coating members have a length of the order of 3 meters or more measured in the direction transverse to the direction of movement of the web this leads to serious problems. Even assuming that such precise manufacturing techniques are employed, it has also been found that temperature variations in the coating composition being dispensed can cause deviations (i.e., "warping") in the straight flat surfaces of the coating members. Such deviations in the contacting surfaces may cause portions of the web to remain uncoated since the dam formed in the nip between the web and the coating member may temporarily disappear due to the warping, especially if a relatively small excess quantity of coating com-position is applied.
BRIEF DESCRIPTION OF THE INVENTION AND OBJECTS
A primary object of the present invention is to provide method and apparatus which eliminates the above-mentioned disadvantages through the utilization of a technique which applies the coating composition on each surface of the web through outlets having orifices along the contact sur-faces of the coating members facing the web and by arranging the aforesaid contact surfaces in a spaced fashion in the direction of the movement of the web.
Thus, according to the present invention, instead of using the arrangement of the prior art in which the opposed coating members are located directly opposite one another, the present invention proposes an arrangement whereby the coating members are displaced with respect to one another relative to the direction of travel of the web, which arrangement consider-ably reduces the need for making the contacting surfaces of the coating members absolutely straight which further serves to reduce the otherwise stringent manufacturing requirements necessary to produce the coating members of the prior art.
In accordance with one embodiment of the subject invention, the supply of the coating agent as well as the positioning of the appropriate contacting surfaces in relation to the ass~ociated surface of the web are set so that an excess dam of coating composition is formed immediately before the nip between the contact surface of each coa~ing member and the associated surface of the web. It has been found that the hydraulic pressure created by the movement of the web and the coating composition deposited thereon serves to stabilize the web so that it floats or is suspended between the opposed layers of coating compositions which acts much like a lubricant in that it facilitates the smooth and stabilized passage of the web between the rigid coating members.
The coating result is further improved if the initial direction of travel of the web i5 altered as the web passes each of the rigid coating members which is accomplished by lateral displacement of the surfaces of the coating members contacting the web, said lateral displacement being transverse to the normal direction of travel of the web. It has been found that this deflection of the web further enhances stabilization of the web which is an important factor when the means proposed according to the present invention is employed as a primary coating station positioned to the upstream side of a pair of opposed flexible doctors which function to spread the coating composition in a uniform manner and scrape off any excess. It is important that the web be stabilized prior to its passage between the flexible doctor since vibrations or the like due to the instability or fluttering of the web passing through the primary coating station will cause the flexible doctors to be deflected from their desired position leading to a non-uniform and hence unacceptable coating layer.
In accordance with another embodiment of the present invention, the entire coating process can be effectively controlled by means of an adjust-able displacement of the coating composition dispensing members after the coating members have been properly positioned against the web.
As has been mentioned hereinabove, it is necessary to form a dam of the coating in order to assure a uniform coating layer devoiding uncoated spots. This is for example accomplished through the utilization of rotatable contact members having elongated dispensing slots whereby the members are adjustable to set the dispensing slots at a suitable angle relative to the web so that the desired quantity of coating composition is supplied to the web and a suitable quantity of coating composition will be dispensed to form the dam with a certain excess amount thereof possibly dripping downwardly from the region of the dam. This complete control of the coating process is thus obtained by adjusting the quantity of coating composition supplied and by aligning the dispensing slots at a suitable angle relative to the web.
The present invention also contemplates means for performing the method described hereinabove through the employment of outlet orifices for the coating composition which are located within the contact surfaces of the coating members positioned against each surface of the web and by staggering the contact surfaces relative to the path of movement of the web.
The present invention is further characterized in that the contact surface of one coating member may be positioned above the opposing contact surface of the other coating member to be arranged in an overlapping fashion thereby causing the path of movement of the web to be altered as it passes each contact surface so that the web moves in an undulating or "zig-zag"
fashion as it passes through the primary coating station.
The contact surfaces of each coating member may be shaped in the form of a pair of lips which taper in the direction of the paper web with the lips surrounding and hence defining the supply channel and outlet orifice for the coating composition.
According to another preferred embodiment of the invention, the contact surfaces of the coating members may comprise tubular members extending substantially across the entire width of the web whereby each tubular member includes an elongated slot-like outlet opening for dispensing a coating agent, which opening extends substantially across the entire width of the web. The tubular members are preferably pivotably journalled and so arranged as to permit adjustable orientation of the outlet slots, which adjustments are independent of the rotatably adjustable contact members.
In the case where it is desired to provide an uncoated marginal portion along each edge of the web, adjustable screening strips may be arranged within the slot-like openings so as to be adjustable displaceable within the slot at the opposing ends thereof.
In order to avoid non-uniform coating of the web due to a pressure drop in the coating agent as it moves toward the outlet slots, the distri-bution chambers for the coating agent are preferably connected by means of a plurality of supply conduits distributed at spaced intervals along the length of the coating members and communicating with an inner chamber located in the lower portion of each coating member, which inner chamber preferably has a greater storage volume than the distribution chamber. The supply conduits may preferably be comprised of flexible plastic tubes or the like.
In order to prevent the coating members from becoming clogged or dirty, the portions of the coating members which comprise the contact sur-faces may be rotatably journalled in holders having intermediate seals. An upper covering plate may also be arranged above each contact surface portion to protect the contact surface portions from excess coating composition which may drip downwardly from upper portions of the web as it leaves the primary coating station.
BRIEF DESCRIPTION OF THE FIGURES
The above as well as other objects of the invention will become apparent when reading the accompanying description and drawings in which:
Figure 1 shows a sectional elevational view of a first embodiment of a coating means designed in accordance with the principles of the present invention;
Figure 2 shows an elevational sectional view of a second preferred embodiment of the present invention;
Figure 3 shows an enlarged detailed view of a portion of one coating member of Figure 2;
Figure 4 is a sectional elevational view of still a third embodiment of the present invention;
Figure 5 shows an enlarged detailed view of a portion of one coating member of Figure 4;
Figure 6 shows a perspective view of a tubular dispensing member of the type shown in Figures 2 - 5 and employing a screening element;
Figure 7 is a perspective view showing the screening element and tubular member of Figure 6 in greater detail; and Figure 8 is a sectional view showing one technique for pivotally mounting the supply container of Figure 2 and 4, for example.
DETAILED DESCRIPTION OF THE INVENTION
The embodiment of Figure 1 shows a paper web 1 which is conveyed in the upward vertical direction shown by arrow A. Although not shown for purposes of simplicity, the movement of the paper web is typically con-trolled by dispensing the untreated paper web from a supply reel typically positioned beneath the apparatus of Figure 1 and winding the subsequently treated paper web upon a wind-up reel typically positioned above the apparatus of Figure 1. The system may further include other guiding rollers, drying members, and the like, which have also been omitted for purposes of simpli-city.
The upwardly moving web passes between coating members 2 and 3 positioned on opposite sides of the paper web. The coating members 2 and 3 are pivotally journalled about longitudinal axes 4a and 5a, for example, by elongated shafts 4 and 5, whose free ends may be journalled within suitable bearings (not shown). The coating members may be rotated to accurately position their respective contact surfaces 6 and 7 by means of coarse and fine adjustment assemblies.
The coating members 2 and 3 are each respectively provided with a hollow interior chamber 8 and 9 containing the coating composition supplied thereto through suitable conduits, not shown. Each of the chambers 8 and 9 is respectively provided with an outfeed channel 10 and 11 communicating with the chambers 8 and 9 and with the contact surfaces 6 and 7 whereby the channels 10 and 11 terminate in the elongated slot-like outlets 12 and 13 positioned between the pairs of lips 14 - 15 and 16 - 17. The contact surfaces of the lips are arranged somewhat obliquely relative to the direction of movement of paper web 1.
The coating members 2 and 3 are preferably set with respect to one another so that the outlets 12 and 13 and the pairs of lips 14 - 15 and 16 - 17 are arranged in staggered fashion relative to the path of movement of the paper web and further so that the contact surfaces overlap one another slightly, i.e. so that they are displaced somewhat relative to the otherwise straight line path of movement of the paper web. Due to this displacement, paper web 1 will be slightly deflected or curved as it passes the contact surfaces 6 and 7.
The coating agent dispensed through the outlet openings 12 and 13 is supplied at a rate sufficient to cause dams 20 and 21 to form between each surface of the paper web and the associated contact surface 6 and 7 of the coating members 2 and 3. Coating composition in excess of that necessary to form the dam runs downwardly under the influence of gravity along the surfaces 18 and 19. The hydraulic pressure created by the excess coating composition contributes to stabilization of the paper web as it passes between coating members 2 and 3 causing the web to float or be suspended between the layers of coating composition which acts in much the same way as a lubrica-ting agent. The formation of the dams further prevents the occurrence of a non-uniform coating caused by formation of air bubbles in the coating compo-sition.
It can readily be understood that the arrangement of the coating members of Figure 1 considerably reduces the requirements that the contact surfaces 6 and 7 be perfectly straight due to the fact that the paper web is somewhat pulled around each contact surface enabling the web to compensate for any uneveness in the straightness of the contact members so that any deviation from the straight flat contact surfaces will not affect the result _ g _ ~054873 of the coating process.
Figure 2 shows another preferred embodiment of the present in~ention in which the contact surfaces 6 and 7 of the embodiment of Figure 1 are replaced by elongated tubular members 22 and 23 which extend along the entire width of paper web 1 and are preferably pivotably journalled in a holder substantially comprised of plates 18 - 24 and 19 - 25 which define the inner and outer sides of coating members 2 and 3. As can best be seen from Figure 3, the above-mentioned plates pivotally hold the tubular members, such as, for example, the tubular member 22 with the aid of brackets 26a and 27a and intermediate seals 26 and 27 preferably secured to the inner surfaces of plates 18 and 24 by clamping brackets 26a and 27a. Each of the tubular members are respectively provided with interior distributing chambers 28 and 29 for receiving the coating compound. Each distributing chamber is in communication with the larger chambers 40 and 41 defined by hollow elongated tubular members 38 and 39, respectively, by means of flexible tubular supply conduits 30 arranged at spaced intervals along the length of each of the members 22 and 23 (note, for example, Figure 7). Each of the tubular members 30, which may preferably be formed of a transparent resilient plastic material, is force-fitted over connection nipples 31 in members 38 and 39 and connection nipples 32 in members 22 and 23.
Tubular members 22 and 23 are each provided with elongated slot-like outlet openings 33 and 34 extending over the entire length of members 22 and 23 and directed toward an associated surface of the paper web.
Tubular members 22 and 23 are preferably pivotable about their longitudinal axes 22a and 23a to such an extent that the position of each outlet can be altered to position slot 33, for example, (see Figure 3) an angular distance a above the solid line position 33 or, alternatively, an angular distance b below solid line position 33. It should further be noted that the tubular members 22 and 23 may be rotated independently of the coating members 2, 3 about their axes of rotation designated by numerals 22a and 23a in Figure 2.
The distance X, shown in Figure 2, represents one suitable vertical displacement between the contact surfaces of the tubular members 22 and 23 measured in the direction of travel of paper web 1.
The arrangement of Figure 2 has the advantage, inter alia, since the tubular members 22 and 23 are rotatably mounted to enable these members to be turnable to some extent independently of each other due to the fact that they are connected to associated members 38 and 39 by flexible tubes 30. The ends of each of the coating members 38 and 39 may be mounted in rotatable seals as shown in Figure 8. End 38a, for example, has a reduced diameter portion 38a encompassed by rotatable seal 50 provided in sidewall 51. The opposite end 38b of member 38 is closed and is pivotally mounted within the opening 52a in side wall 52. If desired, a bearing may be provided between opening 52a and the reduced diameter portion of end 38b. Conduit 53 is coupled to a suitable supply of coating composition.
If desired, the ends of tubular members 22 and 23 may be configured in the manner of end 38b of member 38 so as to be received in openings in side-walls 51 and 52, to further facilitate the ability of members 22 and 23 to revolve, whereby the coating process is entirely under control when in operation. For example, the quantity of coating agent which drips down-wardly along the exterior surfaces of plates 18 and 19 and the quantity of coating agent supplied to the paper web, as well as the formation of dams 20 and 21 of a suitable size, can be set so as to create each dam immediately adjacent the nip formed by the paper web and the portion of the contact surface engaging the web. Another advantage of the arrangement shown in Figure 2 resides in the fact that tubular members 22 and 23 are inexpensive in that they can be manufactured rather simply and hence cheaply. Alter-natively, the tubes need not be perfect cylinders but may, for example, be truncated cylinders having their curved surface portions engaging web 1.
Members having other suitable cross-sectional configurations may also be used in place of tubular members, if desired. In addition, the configuration of the outlet slots may be altered from that shown in Figure 2.
For example, the contact surfaces may consist of lips protruding outwardly from the arcuate surface members 22 and 23 and being spaced from one another so as to define the outlet opening therebetween.
1~54873 Figure 4 shows still another embodiment of the present invention which, while substantially similar to the embodiment of Figure 2, shows the covering plates 24 and 25 as having upwardly extending portions 24a and 25a to enclose a substantial portion of the tubular members 22 and 23 and thereby protect the tubular members from collecting dirt or coating composition which may drip down from above.
Figure 5 shows a more detailed view of the upper portion of coating member 2 in which the seals 26 and 27 of Figure 2 are replaced by scrapers 26' and 27' formed of rubber or flexible steel clamped to the inner surfaces of plate portions 18 and 18a by clamping brackets 18b and 18c. The flexible scrapers prevent coating compound from entering into the hollow interior of coating members 2 and 3.
Figures 6 and 7 show the manner in which coating dispensing slot 33 provided in tubular member 22 may be at least partially sealed or screened off by means of a screening strip 35 which is inserted into slot 33 so as to completely fill lengthwise portion L of slot 33. It should be understood that a similar screening strip may be adjustably positioned within the opposite end of slot 33. Figure 7 shows screening strip 35 inserted into slot 33 so that a marginal portion M of the paper web 1 is maintained free of the coating agent. Obviously, the width of the uncoated marginal portion M may be adjusted by suitable adjustment of the screening strips.
It can be seen from the foregoing description that the present invention provides a novel method and apparatus for substantially simultan-eously coating both sides of a web by means of independently adjustable staggered overlapping contact members which assure uniform distribution of the coating composition over each surface of the web while compensating for any unevenness in the contact members due to the novel zig-zag manner in which the web moves in passing through the coating station by making the contact surfaces and coating composition dispensing slot independently adjustable. Location of the dam of coating can be suitably adjusted so as to be positioned immediately adjacent the nip formed between the web and ~054873 the associated contact surface.
Although there has been described a preferred embodiment of this novel invention, many variations and modifications will now be apparent to those skilled in the art. For example, as was mentioned hereinabove, the coating apparatus can also be used as a primary coating station in con-junction with a secondary scraping station positioned above the primary coating station and comprising two opposed flexible doctors. Also, the means proposed according to the present invention can be utilized to coat opposite sides of the web with different coating compounds. Therefore, this invention is to be limited, not by the specific disclosure herein, but only by the appending claims.
Claims (5)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. A method of applying coating sequentially but substantially simultaneously to both surfaces of a web of indeterminate length moving generally vertically in an upward direction comprising the steps of: passing one surface of the web over a first stationary coating member thereby defining a first nip between the engaging surfaces of said first coating member and said one surface of the web; passing the other surface of the web over a second stationary coating member aligned in a slightly displaced position and overlying the first coating member in a vertical plane in the direction of the movement of the web, thereby defining a second nip between the engaging surfaces of said second coating member and said other surface of the web; arranging the nips in staggered fashion to cause the web to move along a generally undulating path as it passes between the opposed coating members, the coating members cooperating so that the second coating member causes the web to bear on the first coating member and be displaced away from the vertical direction, the first coating member cooperating with the vertical movement of the web to cause the web to bear on the second coating member and be displaced towards the vertical direction; and feeding coating composition through an opening in the coating member located in the region of each nip at a rate sufficient to create a dam of coating composition in each of said nips to significantly reduce any vibration of the web during its movement and thereby stabilize the web to enhance the uniformity of the coating applied thereto.
2. The method of Claim 1, further comprising the step of adjusting the amount of coating composition passing through each nip so that it is less than the amount fed into each nip.
3. The method of Claim 1, further comprising the step of adjusting the positioning of the outlet openings relative to the moving web to uniformly coat each surface of the web to thereby prevent uneven coating.
4. The method of Claim 1, further comprising the step of arranging the outlet openings of the coating members in staggered overlapping fashion to cause the web to move along a generally undulating path as it passes between the opposed coating members.
5. The method of Claim 1 further comprising the step of adjusting the location of the outlet openings for the coating composition subsequent to the completion of step (b) to assure the formation of a dam of excess coating at each nip.
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| SE7401796A SE394963B (en) | 1974-02-11 | 1974-02-11 | SET AND DEVICE FOR TWO-SIDED COATING OF A PAPER PATH |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1054873A true CA1054873A (en) | 1979-05-22 |
Family
ID=20320174
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA219,332A Expired CA1054873A (en) | 1974-02-11 | 1975-02-04 | Coating method and apparatus therefor |
Country Status (10)
| Country | Link |
|---|---|
| JP (1) | JPS5853582B2 (en) |
| AT (1) | AT341879B (en) |
| CA (1) | CA1054873A (en) |
| CH (1) | CH631640A5 (en) |
| DE (1) | DE2504701C2 (en) |
| FI (1) | FI57631C (en) |
| FR (1) | FR2260395B1 (en) |
| GB (1) | GB1483181A (en) |
| IT (1) | IT1031265B (en) |
| SE (1) | SE394963B (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5807434A (en) * | 1993-05-27 | 1998-09-15 | Alcan International Limited | Apparatus for two-sided coating of elongated strip articles |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4390490A (en) * | 1980-04-07 | 1983-06-28 | Teepak, Inc. | Fibrous casing extrusion |
| FI66042C (en) * | 1980-10-08 | 1984-08-10 | Waertsilae Oy Ab | ANORDNING FOER BESTRYKNING AV BANA |
| JPS5927862U (en) * | 1982-08-12 | 1984-02-21 | 日本板硝子株式会社 | coating tank |
| JPS5927863U (en) * | 1982-08-12 | 1984-02-21 | 日本板硝子株式会社 | Paste-like substance coating equipment |
| DE3701941A1 (en) * | 1987-01-23 | 1988-08-04 | Dittberner Gmbh | ORDER HEAD |
| GB2215642A (en) * | 1988-03-17 | 1989-09-27 | David Yu | Apparatus for adhesive tape manufacture |
| US5168731A (en) * | 1991-04-15 | 1992-12-08 | Laura M. A. Vidalis | Continuous foam dyeing apparatus and method |
| US6033726A (en) * | 1993-05-27 | 2000-03-07 | Alcan International Limited | Coating of wax-like materials onto moving strip articles |
| US5622562A (en) * | 1993-05-27 | 1997-04-22 | Alcan International Limited | Coating strip material with protective decorative layers while avoiding use of solvents |
| BR9509911A (en) * | 1994-11-23 | 1997-10-14 | Alcan Int Ltd | Coating of materials such as wax on moving tape articles |
| WO1996015858A1 (en) * | 1994-11-23 | 1996-05-30 | Alcan International Limited | Coating strip material with protective/decorative layers while avoiding use of solvents |
| WO1998042449A1 (en) * | 1997-03-24 | 1998-10-01 | Solipat Ag | Method and device for applying a flowable medium |
| CN105583117B (en) * | 2014-10-21 | 2017-09-15 | 广东金明精机股份有限公司 | Plastic film for agricultural use functional liquid coating blow-dry device |
| CN106964526A (en) * | 2017-05-17 | 2017-07-21 | 深圳市信宇人科技股份有限公司 | Two-sided extrusion coating method and its double spread device based on microporous substrate |
Family Cites Families (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CH407823A (en) * | 1963-11-06 | 1966-02-15 | Lamicoater Establishment | Applicator for paints, varnishes, adhesives and other materials on at least weakly flexible material webs, such as paper, metal and plastic foils or fabrics |
| SE348777B (en) * | 1968-02-08 | 1972-09-11 | Ethyl Corp |
-
1974
- 1974-02-11 SE SE7401796A patent/SE394963B/en not_active IP Right Cessation
-
1975
- 1975-01-29 IT IT1972175A patent/IT1031265B/en active
- 1975-01-30 AT AT69275A patent/AT341879B/en not_active IP Right Cessation
- 1975-02-04 CA CA219,332A patent/CA1054873A/en not_active Expired
- 1975-02-05 CH CH138575A patent/CH631640A5/en not_active IP Right Cessation
- 1975-02-05 DE DE19752504701 patent/DE2504701C2/en not_active Expired
- 1975-02-05 GB GB498075A patent/GB1483181A/en not_active Expired
- 1975-02-07 FR FR7503837A patent/FR2260395B1/fr not_active Expired
- 1975-02-10 FI FI750354A patent/FI57631C/en not_active IP Right Cessation
- 1975-02-12 JP JP1777775A patent/JPS5853582B2/en not_active Expired
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5807434A (en) * | 1993-05-27 | 1998-09-15 | Alcan International Limited | Apparatus for two-sided coating of elongated strip articles |
Also Published As
| Publication number | Publication date |
|---|---|
| FI750354A (en) | 1975-08-12 |
| IT1031265B (en) | 1979-04-30 |
| ATA69275A (en) | 1977-06-15 |
| JPS5853582B2 (en) | 1983-11-30 |
| SE7401796L (en) | 1975-08-12 |
| FR2260395B1 (en) | 1978-07-13 |
| FR2260395A1 (en) | 1975-09-05 |
| DE2504701A1 (en) | 1975-08-14 |
| AT341879B (en) | 1978-03-10 |
| DE2504701C2 (en) | 1984-10-25 |
| FI57631C (en) | 1980-09-10 |
| JPS50117837A (en) | 1975-09-16 |
| FI57631B (en) | 1980-05-30 |
| GB1483181A (en) | 1977-08-17 |
| SE394963B (en) | 1977-07-25 |
| CH631640A5 (en) | 1982-08-31 |
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