US3871326A

US3871326A - Coating material recovering device for air knife type coating apparatus

Info

Publication number: US3871326A
Application number: US371796A
Authority: US
Inventors: Masao Kanda; Akio Watanabe
Original assignee: Fuji Photo Film Co Ltd
Current assignee: Fujifilm Holdings Corp
Priority date: 1972-06-20
Filing date: 1973-06-20
Publication date: 1975-03-18
Anticipated expiration: 1992-03-18
Also published as: JPS4921423A; ES416063A1; DE2331521A1; CA987488A; GB1439960A; JPS5610109B2

Abstract

The present invention relates to a coating material recovering device which is used in an air knife type coating apparatus. A separating plate is located downstream from the air jet flow blown from a slit-like nozzle after the air jet flow has contacted the surface of a web carrying excess coating material and removed the same. A separating chamber is defined below the separating plate for collecting the excess coating material contained in the air jet flow. Additional separating chambers can be provided for better separation. A means for guiding the air jet flow from which the coating material has been removed is also provided.

Description

nited States Kanda et al.

atet [191 COATING MATERIAL RECOVERING DEVICE FOR AIR KNIFE TYPE COATING APPARATUS [75] Inventors: Masao Kanda; Akio Watanabe, both of Fujinomiya, Japan [73] Assignee: Fuji Photo Film Co., Ltd.,

Kanagawa, Japan [22] Filed: June 20, 1973 [21] Appl. No.: 371,796

[30] Foreign Application Priority Data June 20, 1972 Japan 47-061480 52 U.S.C1.Q 118/63, 34/160 [51] Int. Cl. B05c 1I/06 [58] Field of Search. 118/63, 102 R, 102 L, 102 A;

[56] References Cited UNlTED STATES PATENTS 2,679,231 5/1954 Pomper et al. 118/63 3,229,447 l/1966 Kosta 118/63 X 3,397,673 8/1968 Mahoney et a1. 118/63 3,550,553 12/1970 Mahoncy et a1. 118/63 3,611,987 10/1971 Kohler et al. 118/63 Primary ExaminerMorris Kaplan Attorney, Agent, or Firm-Sughrue, Rothwell, Mion, Zinn & Macpeak [57] ABSTRACT The present invention relates to a coating material recovering device which is used in an air knife type coating apparatus. A separating plate is located downstream from the air jet flow blown from a slit-like nozzle after the air jet flow has contacted the surface of a web carrying excess coating material and removed the same. A separating chamber is defined below the separating plate for collecting the excess coating material contained in the air jet flow. Additional separating chambers can be provided for better separation. A means for guiding the air jet flow from which the coating material has been removed is also provided.

4 Claims, 9 Drawing Figures Pmmggm 1 aims 3, 87 1,325

sum 1 0F 3 PRIOR ART PRIOR ART SHLU 2 UP 3 PRIOR ART WATER COATING MATERIAL RECOVERING DEVICE FOR AIR KNIFETYPE COATING APPARATUS BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to coating apparatus for applying a coating material to a travelling web such as paper, plastic film and the like, more particularly, to a device for recovering the coating material in coating apparatus of the air-knife type. The air knife type coating apparatus is a continuous coating apparatus employing a slit shape d air jet nozzle for blowing away excessive coating material applied on the surface ofthetravelling web by a coating means such as a coating roll, a coating slit and the like for making a smooth coating surface on the web. The coating material recovering device recovers the excessive coating material blown away by the air jet nozzle and separates the coating material from the air and discharges the air into the atmosphere.

2. Description of the Prior Art The coating material recovering device employed in air knife type coating apparatus has been called a catch pan," baffle pan or the like, and has heretofore been improved with respect to various points. However, any type of conventional device for recovering coating material has disadvantages in practical use, and the efficiency of the recovering device has not been sufficiently accomplished. Some conventional coating material recovering devices are shown in FIGS. 1 to 4, in which conventional devices as disclosed in US. Pat. Nos. 3,229,447; 3,397,673; 3,550,553 and Japanese Utility Model Publn. 33023/1971 are shown.

In the prior art recovering devices as shown in FIGS. 1 to 4, a travelling web h is fed in contact with a coating rollj by means ofa holder roll i and excess coating material picked up from a coating pan l is applied to the web. The coated web m is fed around a backing roll n and an air jet flow (I is blown thereonto from a slit-like nozzle b of an air doctor a. A separating plate g is provided downstream of the air jet flow (1 (which includes excess coating material c blown away by the air jet) for directing the air jet flow d toward a comparative long guide plate e. Since the air flow including the coating material is not effectively divided into air and coating material by the top end ofthe separating plate g, rather, the coating material is mixed with the jet air flow while the flow is guided along the guide plate e up to a coating material collecting portion f, and particles of coating material are scattered by the air jet flow causing clogging of the air doctor and roughness in the thickness of the coated layer. Further, upon the scattering of coating material the air around the apparatus is contaminated and the life of the apparatus is shortened. The contaminated air is, of course, harmful to the health of the operators of the coating apparatus, and the loss of the coating material due to the scattering of the coating material reduces the efficiency of recovery of the coating material. This is economically a great loss in the operation of the coating apparatus.

Another defect inherent in such apparatus is that the construction of the coating material collecting portion is complicated and it is, accordingly, difficult to clean the inside of the collecting portion of the apparatus.

SUMMARY OF THE INVENTION In light of the above defects of conventional coating apparatus, the principal object of the present invention is to provide a device which effectively recovers excess coating material blown from the surface of a web by an air-jet flowin an air knife type coating apparatus.

Another object of the present invention is to provide a device which effectively separates the coating material from the air flow blown from the air jet nozzle and discharges clean air into the atmosphere.

Still another object of the present invention is to provide a device which prevents fine particles ofthe coating material created during the air knife operation of an air knife type coating apparatus from escaping into the atmosphere.

A further object of the present invention is to provide a coating material recovering device having a simple interior construction which can easily be cleaned by an operator of the coating apparatus.

A still further object of the present invention is to provide a coating apparatus in which the scattering of the coating material staining the slit nozzle of an air doctor is prevented to obtain a smooth surface and uniform thickness of the coated layer.

Yet a further object of the present invention is to provide a coating material recovering device particularly adapted to be used in a high speed air knife type coating apparatus.

The coating material recovering device in accordance with the present invention is provided with a first fluid-air separator and a second fluid-air separator to effectively separate the coating material from the air. The first separator comprises a separating plate which separates the particles of the liquid coating material from the air jet flow utilizing the difference in inertial moment thereof by use of the tip end of the separating plate. The second separator is a means for utilizing the negative pressure made by the air jet flow or suction pressure made by a suction fan to form a second air flow blowing into the coating material recovering portion of the apparatus to direct the air in a different direction. In some embodiments of the present invention, the coating material recovering device is provided with a third separator to enhance the effect of separation of fluid and air.

Other objects, features and advantages of the present invention will be made apparent from the following detailed description of the invention with reference to the accompanying drawings in which:

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1 4 are sectional views of coating material recovering devices of conventional air-knife coating apparatus,

FIG. 5 is a schematic side view showing the arrangement of the apparatus in accordance with the present invention,

FIG. 6 is a vertical sectional view of one coating material recovering device in accordance with the present invention,

FIG. 7 is a side elevational view of the same,

FIG. 8 is a vertical sectional view of a coating material recovering device in accordance with another embodiment of the present invention, and

FIG. 9 is a vertical sectional view of the coating material recovering device in accordance with still another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to FIG. 5 showing the overall arrangement of the apparatus of the present invention, a continuously travelling web 1 is brought into contact with a coating roll 3 by use of a holder roll 2 and fed around a backing roll 7, where excess coating material applied on the surface of the web 6 by means of a coating pan filled with coating material 4 is blown from the surface of the web 6 by means of a high speed airjet flow ejected from a slit-shaped nozzle 9 of an air doctor 8. Thus, a web bearing a coating layer of the predetermined thickness is obtained. The coating material blown away from the surface of the coated web 10 by means of the air jet flow is collected by a coating material recovering device 100 which has a pair of

ducts

101, 102 provided with

dampers

103, 104 for controlling the distribution of air or the flow rate through the coating recovering device 100. The

ducts

101 and 102 communicate with a single duct 105 which in turn is connected with a fine particle removing device 106 which removes extremely fine particles by use of a water shower. The fine particle removing device 106 is connected with a suction fan 107 which pulls the air jet through damper 108, which in turn controls the pulling pressure to provide optimum coating conditions such as coating speed, amount of coating material and so forth.

A preferred embodiment of the present invention is shown in FIGS. 6 and 7. A travelling web 1 is fed around a holder roll 2 and brought into contact with a coating roll 3 thereby so that the coating material 4 in a coating material pan 5 is applied to the surface of the web 1 forming a coated web 6. The web 6, bearing excess coating material, is further fed around a backing roll 7 where the web 6 is subjected to a high speed air jet flow ejected from the slit-like nozzle 9 of the air doctor 8 so that the excess coating material is blown off the surface of the web 6 to provide a web 10 bearing a predetermined thickness of the coating material. The coating material removed from the surface of the web 6 by the high speed air jet flow ejected through the slit nozzle 9 of the air doctor 8 is discharged into the atmosphere together with the air jet fiow through a coating material recovering device, in which the flow 11 mainly composed of coating material is first divided into air and coating material in the first separating chamber 13. The air flow including the coating material in the shape of particles flows along a separating plate 12 and the coating material of large specific gravity falls downward from the lower end ofthe separating plate 12 into the first separating chamber 13. The air which comes down behind the first separating plate 12 moves slowly in the first separating chamber 13, during which time the fine coating material component thereof falls down into the collected coating material on the bottom of the first separating chamber 13. The air jet flow 15 flowing downward along the separating plate 12 advances further below the separating plate 12. Thus, the first separation ofthe air from the coating material is completed.

A part of the excessive coating material mingled in the air jet flow is particulated into fine particles and guided into the second separating chamber 17 together with the air jet flow 15. The air jet flow 15 containing fine particles and flowing along the separating plate 12 hits the wall 16 of the device and moves downward along the interior surface of the wall 16 into the second separating chamber 17 provided downstream the guide wall 16. The air jet flow containing fine particles 18 is lowered in speed when the flow comes into the chamher 17. When its direction of advancement changes, particles of a comparatively large specific gravity 19 are collected on the bottom of the second separating chamber 17. The coating material 20 collected on the bottom of the second separating chamber 17 is discharged through a discharge port 21.

As will be apparent to one skilled in the art, the fields of use of the apparatus present invention are not limited in any manner whatsoever, and it can be used to recover substantially any commonly coated material which is amenable to air knife coating, including separating fine particles as small as on the order of several microns from particles of a comparatively high specific gravity, for instance, in the range of 0.3 to 3.

Further, the air jet flow 22 containing an extremely small amount of fine particles advances along the interior surface of an outer wall 23 opposite to wall 16 and hits the bottom wall 24 of the first separating chamber 13 and changes its direction of advancement and is guided into a third separating chamber 27 defined by

internal walls

25 and 26. When the air jet flow 28 flowing into the third separating chamber 27 changes its direction of advancement therein, a part of the coating material having a comparatively large specific gravity 29 is collected on the bottom of the third chamber and is discharged out of discharge port 30. On the other hand, clean air from which the coating material has been removed is dishcarged from duct 31 provided on the side wall of the third separating chamber 27.

Further, if a container 32 forming the third separating chamber 27 is fixed to a frame 33 and the body portion 34 of the coating material recovering device 34 is made movable on a rail 37 with

wheels

35 and 36 provided thereon from the position shown in H6. 6 to the left,

external covers

38 and 39 and an internal cover 40 can be easily removed together with side cover 41 to make the cleaning of the coating material recovering device easy.

FIG. 7 is a side elevation of the coating material recovering device in accordance with the present invention as shown in FIG. 6, in which a travelling web 1 is brought into contact with a coating roll 3 by means of a holder roll 2 and a coating material is applied onto the surface of the web from a coating material pan 5. The web 6 coated with the coating material is fed around a backing roll 7, where a high speed air jet flow ejected from a slit nozzle 9 of the air doctor 8 is blown against the surface of the web 6 fed around the backing roll 7 to remove excess coating material and the air jet flow flows along a separating plate 12 and the coating material is discharged from discharging port 14 and recovered. The separating plate 12 is moved by an air cylinder 43 provided on a side plate 42 of the coating material recovering device by way of a crank 44 to control the spacing between the end of the separting plate 12 and the backing roll 7. The spacing is selected by adjusting a stopper 45 which restricts the movement of the crank 44. On both sides of the coating material recovering device on the end plates 42 are provided side covers 41 having a duct communicating opening 31, respectively, to discharge air which has been cleaned through the first, second and third separating chambers. The side covers 41 are easily removable for cleaning the interior of the coating material recovering device. Further, in order to facilitate the inspection and cleaning ofthe interior of the coating material recovering device, exterior covers 38 and 39 are made removable and the whole body 34 of the device is made horizontally slidable on the rail 37 (leaving the second separating chamber 17).

Another embodiment is shown in FIG. 8, wherein a continuously travelling web 6 carrying excess coating material is fed around a backing roll 7. A high speed air jet flow is ejected from a slit-like nozzle 9 of an air doctor 8 and blown against the surface of the'web 6 travelling around the backing roll 7 to remove excess coating material 50 therefrom. The coating material 50 blown off the web 6 flows along a separating plate 52 together with the air jet 51. At the end of the separating plate 52, the coating material 50 having a comparatively large specific gravity is introduced into the first separating chamber 53 and discharged from the device through discharge port 54 and pipe 55 for recovery. On the other hand, the air jet 51 flows along the separating plate 52 down to the second separating chamber 59. During the falling of the airjet flow 51 down to the second chamber 59 along partition 56, a portion of the fine particles of the coating material 57 flowing on the partition 56 with the air jet are collected by the second separating chamber 59, which is provided for collecting the liquid particles 57 without obstructing the flow of the air jet 58. The particles collected in the second chamber 59 are discharged from the device for recovery.

Reference numerals

60 and 61, respectively, indicate third and fourth separating chambers defined by

partitions

62 and 63 and

outer walls

64 and 65 which collect the

coating material

66 and 67 and discharge the collected material out of the device through discharging

ports

68 and 69, respectively. The air cleaned through the first to fourth separating effect is discharged into the atmosphere through a duct 70.

Another embodiment of the present invention is shown in FIG. 9, wherein a coated web 6 travelling around a backing'roll 7 is subject to an air jet flow ejected from a slit-like nozzle 9 of an air doctor 8 and coating material 80 is blown from the coated surface of the web 6 and guided along a separation plate 82 together with the air jet 81. At the end ofthe separating plate 82, the coating material 80 is introduced into a first separating chamber 83 located behind the separating plate 82. The collected coating material in the first separating chamber 83 is discharged from the device through a discharge port 84 and a pipe 85 for recovery. On the other hand, the air jet flow 81 flows along the surface of a partition 86 extending downstream from the separating plate 82 and goes into a second separating chamber 89 formed by the partition 86 and the

outer portion

87, 88 for separation of fine particles 90 which have not been collected in the first separating chamber 83. The collected fine particles 90 are discharged from the discharge port 91 into the air, and the clean air 92 is discharged through a duct 93.

While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

What is claimed is:

l. in a coating apparatus, means for removing and recovering excess coating material from a web coated in an air knife coating apparatus, said removing and re- 6 covering apparatus comprising:

a. means for applying a flowing gas stream tangentially to the web for removing excess coating material from the web which is entrained in the flowing gas stream;

b. a separating plate adjacent said web extending transversely to the flow path of the flowing'gas stream containing the excess coating material downstream of the contact area of the flowing gas stream with the web for separating excess coating material from the flowing gas stream;

c. a drip pan underlying said separating plate to catch liquid material flowing downwardly on the separating plate undergravity influence;

d. means including said drip pan forming a first chamber for recovery of said excess coating material, the improvement wherein:

e. said first chamber includes chamber wall means to the side of said separating plate opposite the means applying the flowing gas stream, spaced from said plate and extending from said drip pan to the vicinity of said web to form with said drip pan and said separating plate a volume in which separated air moves slowly downwardly behind the separating plate to cause the fine coating material component thereof to gravity deposit into said underlying drip pan; and wherein f. said separating plate is positioned with respect to said gas stream, said web and said drip pan such that the flowing gas stream does not directly enter said first chamber and re entrain substantial amounts of already separated coating material during gravity deposit from said separating plate into said drip pan.

2. Apparatus as defined in claim 1 further comprising wall means disposed generally in line with said separating plate, and extending downwardly from said drip pan in the direction of flow of said gas stream after deflection by said separating plate to guide the air downstream of said first chamber, and said apparatus further comprising additional liquid collecting means, said means comprising a trough located on said guide wall at a location which does not obstruct the flow of air along said guide wall.

3. Apparatus as defined in claim 1 further comprising means for discharging the air jet flow from said apparatus after the coating material has been removed, said discharging means being provided on at least one side of said apparatus for discharging said air flow into the atmosphere.

4. Apparatus as defined in claim 1 further comprising a second separating chamber provided downstream and below said first separating chamber including coating material collecting means at the bottom portion thereof, said second chamber being separable from said first separating chamber, and wherein said first separating chamber includes wheels operatively coupled thereto for moving said first chamber laterally relative to said underlying separating chamber and said apparatus further comprising means for fixing said second separating chamber to a stationary base member upon

Claims

1. In a coating apparatus, means for removing and recovering excess coating material from a web coated in an air knife coating apparatus, said removing and recovering apparatus comprising: a. means for applying a flowing gas stream tangentially to the web for removing excess coating material from the web which is entrained in the flowing gas stream; b. a separating plate adjacent said web extending transversely to the flow path of the flowing gas stream containing the excess coating material downstream of the contact area of the flowing gas stream with the web for separating excess coating material from the flowing gas stream; c. a drip pan underlying said separating plate to catch liquid material flowing downwardly on the separating plate under gravity influence; d. means including said drip pan forming a first chamber for recovery of said excess coating material, the improvement wherein: e. said first chamber includes chamber wall means to the side of said separating plate opposite the means applying the flowing gas stream, spaced from said plate and extending from said drip pan to the vicinity of said web to form with said drip pan and said separating plate a volume in which separated air moves slowly downwardly behind the separating plate to cause the fine coating material component thereof to gravity deposit into said underlying drip pan; and wherein f. said separating plate is positioned with respect to said gas stream, said web and said drip pan such that the flowing gas stream does not directly enter said first chamber and reeNtrain substantial amounts of already separated coating material during gravity deposit from said separating plate into said drip pan.

4. Apparatus as defined in claim 1 further comprising a second separating chamber provided downstream and below said first separating chamber including coating material collecting means at the bottom portion thereof, said second chamber being separable from said first separating chamber, and wherein said first separating chamber includes wheels operatively coupled thereto for moving said first chamber laterally relative to said underlying separating chamber and said apparatus further comprising means for fixing said second separating chamber to a stationary base member upon which said wheels ride.