US3751823A

US3751823A - Drying apparatus

Info

Publication number: US3751823A
Application number: US00205505A
Authority: US
Inventors: F Hansen
Original assignee: Multitec AG
Current assignee: Multitec AG
Priority date: 1970-12-09
Filing date: 1971-12-07
Publication date: 1973-08-14
Anticipated expiration: 1990-08-14
Also published as: CH545659A; CA950189A; DE2155386A1; FR2117468A5; NL7116882A; IT945360B; DE2101787A1

Abstract

The invention concerns drying apparatus suitable for drying strip material, which comprises a drying chamber through which strip material may be passed, a strip entrance and exit aperture in the chamber to allow passage of strip material into and out of the drying chamber, a plurality of rotatable support rolls being disposed in parallel and spaced apart relationship to define a cylindrical cage within the chamber and over which strip material may be passed, means cooperating with the rolls of the cage to enable strip material passing thereover to be supported by a part of the peripheral surface of each roll of the cage and drying means for drying strip material passing over the rolls of the cage.

Description

ited States Patent ansen Aug. M, 1973 [54] DRYKNG APPARATUS 3,638,330 2/1972 Stout 34/156 l Wtier- [75] Inventor E2? Ernst nansenlmgen S Pnmary Examiner-Carroll B. Donty, .lr. WW H W Assistant E qminer Larr y l. c&u arta V [73 Assignee: Multitec A. (1., Canton of Berne, Attor eys-1 F. Obkm Irwln McClelland Switzerland l l;

221 Filed: Dec. 7, 1971 [57] 11 [211 App]. No.: 205,505 The invention concerns drying apparatus suitable for drying strip material, which comprises a drying chamher through which strip material may be passed, a strip [30] Applisafion pfiority Data entrance and exit aperture in the chamber to allow pas- Dec. 9, 1970 Switzerland 18226 sage of strip material into and out of the drying cham her, a plurality of rotatable support rolls being disposed [52] US. Cl. 34/155, 34/160 in parallel and Spaced apart relationship to define a [51] Int. Cl. F26b 9/00 lindrisal cage within the chamber and over which strip [58] Field of Search 34/115, 155, 122, material may be passed, means cooperating with the 34/160 240 rolls of the cage to enable strip material passing thereover to be supported by a part of the peripheral surface References Cited of each roll of the cage and drying means for drying UNITED STATES PATENTS strip material passing over the rolls of the cage.

44,402 9/1864 Cummings et a1 34/155 1.1.; 703,044 6/1902 Crowell 34 155 10 C 10 Drawing Fawn-es 772,694 10/1904 Crowell 34/155 2,624,573 l/1953 Rice 34/155 PAIENIEB AUG] 4 1915 saw 2 or 3 DRYING APPARATUS BACKGROUND OF THE INVENTION 1. Field of invention The present invention relates to drying apparatus, and more specifically to apparatus suitable for drying coatings on strip material,particularly on paper and foil.

2. Description of the Prior Art Apparatus for coating and drying strip material have been known for some time. For drying, hot air-jet driers optionally in combination with IR. irradiation heaters, have been employed.

Many coatings are often required on one or both sides of the strip material, especially in the paper and foil manufacturing industry and also in the production of light sensitive reproduction materials, wherein it is desirable that one coating be completely dry before the next coating is applied. During the drying operation, physical contact with a freshly applied coating is clearly to be avoided.

in the known apparatus, the coated strip material, with the freshly coated side facing upwards, is led through a drying chamber in such a way that the dry underside is lead over support rolls, which rolls may be driven or freely rotatable. However, it is often observed with strip material, particularly paper, that when damp, the strip tends to curl in along the edges and become distorted, whereby longitudinal folding of the strip is prone to occur. This tendency is greater the smaller the supporting surface on the peripheral surface of each support roll and the greater the distance between the supporting rolls. It is possible to increase the supporting surface of each roll by directing the strip material through a large angle around the roll. However, this results in larger distances between support rolls. In known drying apparatus, these disadvantages have been reduced or avoided by arranging the rolls of the drying chamber in the form of an arc and by employing small diameter supporting rolls in close together relationship.

In order to provide for continuous coating involving a plurality of coats with associated intermediate and final drying of the coats, two or more of such drying chambers as herinbefore described and having strip paths of arcuate form have been used in one-above-theother relationship. On each side of at least the first drying chamber, a coating means has been arranged together with a system of rolls for directing the strip from one drying chamber to the other. Generally, the strip material passes under a first coating means wherein a coating is applied to one side thereof and thence through a first drying chamber having rolls arranged as hereinbefore described. The strip material then passes to a system of rolls wherein it is directed to a second coating means wherein a coating is applied to the other side of the strip and thence to a second such drying chamber. By this means, coating and drying of the coating, on each side is possible. By analogous means, it is possible to direct the strip material such that the second coating is applied to the dry first coated side and theoretically, it is also possible to direct the strip material such that a plurality of coats are applied to both sides of the strip material. However, since the strip material cannot cross itself and cannot be supported on a freshly coated side, such an arrangement becomes 2 complicated, space consuming and generally impractical.

Another known form of coating and drying apparatus has many drying chambers arranged lying in a plane, coating means being provided ahead of each drying chamber. The drying chambers in such an apparatus comprise a series of rolls, the axes thereof being arranged in a plane. By directing the coated and dried strip material by means of an appropriate system of rolls, it is possible to program the coatings to achieve consecutive coatings on one side, or alternately on each side, intermediate dryings being effected between coatings. it is clear that such an arrangement has the disadvantage that a large amount of ground space is required because of the planar arrangement of drying chambers and intermediate strip directioning roll systems, and also the disadvantages abovementioned associated with the lack of support of linearly arranged rolls within the drying chambers causing curling and distortion of the strip material and leading to longitudinal folding thereof.

Furthermore both of the aforementioned known drying apparatus exhibit a further disadvantage when employing hot air-jet heaters. It is a requirement in drying strip material by means of hot air-jet heaters that the air jet flow and also that the resulting part-saturated air flow be evenly distributed over the surface of the strip. One general method of satisfying this requirement is by employing a partially sealed air circulation system whereby some of the part-saturated exhaust air is discharged to the atmosphere and the system is replenished with fresh air, the mixture being heated up in a heater and led to the nozzles of the hot air jet drier. It is established technically that to obtain an absolutely even flow pattern in flat or circular chambers of rectangular cross-section such that no air congestion, resulting in zeroflow, occurs, is extremely difficult. it is also established that wetting of, e.g. paper strip, in a coating process, causes curling of the edges and that this phenomenon is reversed during drying so that the edges curl towards the uncoated side. As the supporting rolls are disposed under the uncoated side of the strip material, it will be appreciated that there is a great danger of the curled underside of the strip getting squashed between the strip itself and the rolls. This problem is particularly applicable to drying chambers of planer construction since there is minimal supporting surface beneath the strip material and also air congestion zones of zero net air flow tend to be caused.

To avoid the abovementioned disadvantages, different proposals have been put forward, e.g. by a complicated arrangement of the jets, all of which are complex, expensive and are not capable of general application.

SUMMARY OF THE llNVENTlON It is an object of the present invention to provide a drying apparatus which may be employed in conjunction with known coating means to overcome or substantially to reduce the aforementioned disadvantages.

Accordingly, the present invention provides a drying apparatus suitable for drying coated strip material, which comprises a. a drying chamber through which strip material may be passed,

b. means defining a strip entrance and exit aperture in the drying chamber to allow passage of strip material into and out of the drying chamber,

c. a series of support rolls being disposed in parallel and spaced apart relationship to define a cylindrical cage within the chamber and over the rolls of which, strip material may be passed,

d. means cooperating with the rolls of the cage to enable strip material passing thereover to be supported by a portion of the peripheral surface of each roll of the cage, and

e. drying means for drying strip material passing over the rolls of the cage.

Preferably, the drying means is a hot air-jet drier comprising a plurality of nozzles arranged in a cylindrical surface within the drying chamber radially outwardly of the cage and directed radially inwardly, an air outlet pipe extending from the drying chamber, an air inlet pipe for conducting hot air to the nozzles, an air heater for heating the air before passage thereof through the air inlet pipe, an air pump for pumping air to the air heater, and an air connecting pipe through which air may pass from the pump to the heater. In addition, the air outlet pipe may be connected to the pump such that some at least of the air passing from the drying chamber through the outlet pipe is recycled through the inlet pipe. Generally, it is preferred that the nozzle comprise slits extending axially in the radially inner surface of a hollow cylindrical jacket, the air inlet pipe communicating with the jacket.

The drying apparatus of the invention may be employed in conjunction with any known coating means, e.g. a coating roll and an air brush with the associated counter roll.

The cylindrical arrangement of the supporting rolls allows the advantage of a circular strip material path through the drying apparatus and over the support rolls,allowing on the one hand extremely satisfactory support of the strip material on the support rolls, whereby the dangers of distortion and longitudinal curling and folding are much reduced, and on the other hand much reduced ground space, e.g. in an apparatus enabling one or two coats to be applied and dried, the length of the apparatus as compared to the length of known apparatus of similar capacity is reduced to as much as one third of that length.

As opposed to drying chambers having rollers arranged in linear or arcuate formation, the strip material is led into and passes out of the same aperature in the drying chamber. In the case where hot air-jet drying means are employed, the arrangement of the nozzles to be directed radially inwardly overcomes or substantially reduces the hereinbefore disadvantages of air congestion and zones of zero air flow, the hot air being supplied and distributed over the whole periphery of the strip and flowing evenly against the strip.

Drying and coating apparatus may incorporate any number of units of drying apparatus constructed in ac cordance with the present invention. Generally, three such units are found to be convenient wherein eight variations with respect to the number and sequence of coatings is possible. Naturally, the number of drying apparatus units employed will depend on the particular requirements and may be either increased or decreased as circumstance demands.

In the case wherein the drying apparatus of the present invention is provided with its own air circulation and heating system, this has the advantage that in a coating and drying apparatus embodying more than one heating unit, individual heating temperatures can be set by thermostatic regulation allowing the inlet and outlet air temperatures to be controlled automatically.

Further objects and advantages will appear from the following description of a preferred embodiment of the invention, and the novel features will be particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic, part-sectional view of a drying apparatus of the preferred embodiment,

FIG. 2 is a schematic sectional view along the line A-A of FIG. 1, and

FIGS. 3 to 10 are diagrammatic views of various coating and drying apparatus incorporating at least one of the drying apparatus of the preferred embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the drawings, identical parts bear identical reference numerals.

The drying apparatus of the preferred embodiment shown in detail in FIGS. 1 and 2, comprises a drying chamber 4. Mounted within the drying chamber 4 are a series of support rolls 3 disposed in parallel and spaced apart relationship to define a cylindrical cage, shown more clearly in FIG. 2. Radially outwardly of the cage, and embodying part of the wall of the drying chamber is a hollow cylindrical jacket 7 provided on the radially inner wall thereof with a plurality of slits 5 extending axially across virtually the length of the wall, these slits constituting hot air-jet nozzles and being directed radially inwardly. An aperture, in the form of a slot, in the drying chamber 4 and jacket 7 allows communication of the roll cage with the exterior to permit passage of strip material 2 into and out of the chamber. The lengths l of strip material entering and leaving the drying chamber 4 is shown in FIG. 2 A nip roll 20 cooperating with the terminal roll of the roll cage adjacent the slot serves to enable the strip material to be supported over substantially the whole length thereof by the roll cage. Along the axis or the roll cage extends an air outlet pipe 8 which projects a part way into the chamber 4, and runs from the chamber 4 to a pump 10. The end 9 of the outlet pipe 8 may be disconnected from the pump 10. The pump 10 is connected to an air heater 12 by means of a connecting pipe 11. Running off the connecting pipe 11 is a discharge duct 14 provided with a butterfly valve 15. The air heater is connected to the jacket 7 by means of an air inlet pipe 13 which is connected to the chamber 4 at junction 6. In one end face of the chamber 4, opposite the mouth of the outlet pipe 8 and lying along the axis of the roll cage is an air inlet aperture 16 provided with valve means in the form of a grid of parallel shutters of adjustable inclination.

The operation of the drying apparatus of the preferred embodiment will now be described.

Freshly coated strip material 2 is led into the drying chamber through the slot therein, around the roll cage between nip roll 20 and the terminal roll of the roll cage and out again through the slot in the drying chamber.

I-Iot air is fed to the jacket 7 through inlet pipe 13 from heater 12. The hot air is distributed generally evenly around the jacket 7 and is then forced through the slits 5 to impinge on the continuously moving length of strip material 2. Partially saturated air travels generally radially inwardly of the chamber 4 and the vortex so formed around the projecting mouth of the outlet pipe 8 is sucked out through the outlet pipe 8 to the pump. Some of this same air passes from the pump through the connecting pipe 11 to the heater 12 to be once more cycled through the system. However, a certain proportion of this air is discharged through the discharged duct M into the atmosphere. The amount of air discharged in this manner may be controlled by adjustment of the butterfly 15. Pressure in the drying chamber may be restored by admittance of air through the air inlet aperture 16, and a balance may be achieved by adjustment of the shutter inclination thereof. It will be appreciated that a condition of balance may be achieved with relative ease whereby all air discharged through discharge duct 14 is replenished by air entering through the shutter grid of the air inlet aperture 16. In this condition, substantially no air is lost through the strip inlet and outlet slot in the drying chamber such that all air flow is generally evenly distributed radially inwardly of the chamber.

The above described air circulation system has the advantage that by suitable adjustment of the shuttersof aperture 16 and butterfly 15, such that no net flow of air takes place through the strip material inlet and outlet slot in the drying chamber, the aerodynamic flow pattern within the drying chamber is substantially symmetrical and even.

The above described air circulation and drying system is applicable to the drying of water-based coatings. When it is desired to dry out coatings based on other solvents or supporting media, the end 9 of the air outlet pipe is sealed to prevent air outlet, and the inlet to the pump is opened to the atmosphere. The butterfly 15 is closed and the shutters of aperature l6 opened. If desired the aperture 16 is connected to a condenser (not shown). In use,air from the atmosphere is passed into the drying chamber via inlet pipe 13 and part saturated air passes out of the chamber through aperture 16 wherein, when a condenser is fitted, solvent may be removed from the outgoing air.

In a modification of the drying apparatus of the above described embodiment, an alternative strip material inlet and outlet slot in the drying chamber is also provided in the other side thereof as shown in the broken line FIG. 2. For this purpose nip roll a is required, operating in an analogous manner to nip roll 20 hereinbefore described.

To illustrate the utility of the drying apparatus of the preferred embodiment, coating and drying apparatus embodying as a unit or units the above described drying apparatus will now be described with reference to FIGS. 3 to 10.

Strip take off reels 18 are arranged to allow strip material 2 to be fed to a coating means 17 and via a drying apparatus to a take up reel 19. More than one coating means 17 and drying apparatus units may be employed.

The coating and drying apparatus shown in FIGS. 9 and 10 illustrated the manner in which a system comprising three drying apparatus units may be arranged to coat and dry coatings and the coating possibilities of such an apparatus.

FIGS. 3 and 4 show a path of strip material suitable for applying and drying a coating on one side only of the strip material;

FIG. 5 shows a path of strip material suitable for applying and drying two coatings on one side only of the strip material;

FIG. 7 shows a path of strip material suitable for applying and drying three coatings on one side only of the strip material;

FIG. 6 shows a path of strip material suitable for applying and drying one coating on each side of the strip material; and

FIGS. d, 9 and 10 show a path of strip material suitable for applying and drying two coatings on one side and one coating on the other side of the strip material.

Whilst the preferred form of the present invention has been described, changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of the invention.

What is claimed is:

l. Drying apparatus suitable for drying coated strip material which comprises a. a drying chamber through which strip material may be passed,

0. A series of support rolls being disposed in parallel and spaced apart relationship to define a cylindrical cage within the chamber and over the rolls of which strip material may be passed,

e. hot air jet drying means for drying strip material passing over the rolls of the cage comprising a plurality of nozzles arranged in a cylindrical surface within the drying chamber radially outwardly of the cage and directed radially inwardly, an air outlet pipe having one end extending from the drying chamber and its other end extending into'the drying chamber part way along the cylindrical axis of the cage, an air inlet pipe for conducting hot air to the nozzles, an air heater for heating the air before passage thereof through the air inlet pipe, an air pump for pumping air to the air heater and an air connecting pipe through which air may pass from the pump to the heater.

2. The drying apparatus of claim I wherein the means cooperating with the rolls of the cage comprises a nip roll cooperating with the terminal roll adjacent the means defining an aperture in the drying chamber and around which nip roll strip material may be directed to pass out of the chamber.

3. The drying apparatus of claim 1 wherein said nozzles comprise slits extending axially in the radially inner surface of a hollow cylindrical jacket, the air inlet pipe communicating with the jacket.

4. The drying apparatus of claim it wherein the air outlet pipe is connected to the pump such that at least some of the air passing from the drying chamber through the outlet pipe is recycled through the inlet pipe.

5. The drying apparatus of claim d wherein the drying means includes an air discharge pipe extending from said connecting pipe through which some of the air received from the pump may be discharged to the atmosphere and means defining an air inlet aperture in the drying chamber disposed substantially opposite the mouth of the air outlet pipe within the chamber and along the axis thereof.

6. The drying apparatus of claim wherein the discharge duct and means defining an air inlet aperture are each provided with valve means so as to enable control of discharge and inlet of air respectively.

7. The drying apparatus of claim 3 wherein the valve means in the discharge duct is an adjustable butterfly valve.

8. The drying apparatus of claim 3 wherein the valve means in the means defining an air inlet aperture comprises a grid of parallel shutters of adjustable inclination.

9. Coating and drying apparatus comprising the drying apparatus of claim 1 in combination with at least one coating means. i I

10. Drying apparatus suitable for drying coated strip material comprising:

a drying chamber through which strip material may be passed;

an aperture in the drying chamber defining a common entrance and exit for said strip material to allow passage of said strip material into and out of said drying chamber;

a series of support rolls being disposed in parallel and spaced apart relation to define a cylindrical cage within said drying chamber and over the rolls of which said strip material may be passed;

means cooperating with the rolls of said cylindrical cage to enable strip material passing thereover to be supported by a portion of the peripheral surface of each of the rolls of said cage; and

drying means for drying said strip material passing over the rolls of said cylindrical cage comprising a plurality of hot air nozzles arranged in a cylindrical pattern within said drying chamber radially outwardly of said cylindrical cage and being directed radially inwardly; an air outlet pipe from said drying chamber; and means for conducting hot air to said nozzles.

Claims

1. Drying apparatus suitable for drying coated strip material which comprises a. a drying chamber through which strip material may be passed, b. means defining a strip entrance and exit aperture in the drying chamber to allow passage of strip material into and out of the drying chamber, c. A series of support rolls being disposed in parallel and spaced apart relationship to define a cylindrical cage within the chamber and over the rolls of which strip material may be passed, d. means cooperating with the rolls of the cage to enable strip material passing thereover to be supported by a portion of the peripheral surface of each roll of the cage, and e. hot air jet drying means for drying strip material passing over the rolls of the cage comprising a plurality of nozzles arranged in a cylindrical surface within the drying chamber radially outwardly of the cage and directed radially inwardly, an air outlet pipe having one end extending from the drying chamber and its other end extending into the drying chamber part way along the cylindrical axis of the cage, an air inlet pipe for conducting hot air to the nozzles, an air heater for heating the air before passage thereof through the air inlet pipe, an air pump for pumping air to the air heater aNd an air connecting pipe through which air may pass from the pump to the heater.

2. The drying apparatus of claim 1 wherein the means cooperating with the rolls of the cage comprises a nip roll cooperating with the terminal roll adjacent the means defining an aperture in the drying chamber and around which nip roll strip material may be directed to pass out of the chamber.

4. The drying apparatus of claim 1 wherein the air outlet pipe is connected to the pump such that at least some of the air passing from the drying chamber through the outlet pipe is recycled through the inlet pipe.

5. The drying apparatus of claim 4 wherein the drying means includes an air discharge pipe extending from said connecting pipe through which some of the air received from the pump may be discharged to the atmosphere and means defining an air inlet aperture in the drying chamber disposed substantially opposite the mouth of the air outlet pipe within the chamber and along the axis thereof.

6. The drying apparatus of claim 5 wherein the discharge duct and means defining an air inlet aperture are each provided with valve means so as to enable control of discharge and inlet of air respectively.

9. Coating and drying apparatus comprising the drying apparatus of claim 1 in combination with at least one coating means.

10. Drying apparatus suitable for drying coated strip material comprising: a drying chamber through which strip material may be passed; an aperture in the drying chamber defining a common entrance and exit for said strip material to allow passage of said strip material into and out of said drying chamber; a series of support rolls being disposed in parallel and spaced apart relation to define a cylindrical cage within said drying chamber and over the rolls of which said strip material may be passed; means cooperating with the rolls of said cylindrical cage to enable strip material passing thereover to be supported by a portion of the peripheral surface of each of the rolls of said cage; and drying means for drying said strip material passing over the rolls of said cylindrical cage comprising a plurality of hot air nozzles arranged in a cylindrical pattern within said drying chamber radially outwardly of said cylindrical cage and being directed radially inwardly; an air outlet pipe from said drying chamber; and means for conducting hot air to said nozzles.