US3510960A

US3510960A - Vertical drying machine

Info

Publication number: US3510960A
Application number: US735087A
Authority: US
Inventors: Hisayoshi Kubodera
Original assignee: Individual
Current assignee: Individual
Priority date: 1967-06-10
Filing date: 1968-06-06
Publication date: 1970-05-12
Anticipated expiration: 1987-05-12
Also published as: DE1778826A1; GB1234956A

Description

HISAYOSHI KUBODERA 3,510,960

VERTICAL DRYING MACHINE May 12, 1970 2 Sheets-Sheet 1 Filed June 6, 1968 FIG.

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y 1970 HISAYOSHI KUBODERA 3,510,960

VERTICAL DRYING MACHINE 2 Sheets-Sheet 2- Filed June 6, 1968 FIG. 2

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BY mum United States Patent Office 3,510,960 VERTICAL DRYING MACHINE Hisayoshi Kubodera, 19-10 2-chome, Shinbashi, Minato-ku, Tokyo-to, Japan Filed June 6, 1968, Ser. No. 735,087 Claims priority, application Japan, June 10, 1967, 42/36 66 Int. Cl. F26b 13/00 US. Cl. 34-155 9 Claims ABSTRACT OF THE DISCLOSURE A vertical drying chamber containing a heating device is vertically passed through by a strip material to be dried. The strip runs along an inverted U-shaped path in the chamber over a strip guide roller located at. the top of the drying chamber. Below the guide roller and above the top of the drying chamber, there are provided transverse air curtain creating nozzles which direct air onto the surface of the runs or spans of the strip and prevent heat transfer and leak of fluid from the chamber to the rollers.

BACKGROUND OF THE INVENTION This invention relates to drying machines and, more particularly, to a drying machine of the vertical type having a drying chamber or tower through which a material to be dried is passed.

In a typical example of the drying machine of the above type, the vertical drying chamber has at the upper portion thereof a horizontal guide roller, and a strip material to be dried is continuously passed through the drying chamber in an inverted U-shaped path with the uppermost part of the U-shaped material passing over the guide roller. The material to be dried may, for example, be one wvhich has been passed through a bath of a treating medium dissolved in a solvent.

Such drying machines of the vertical type have various advantages over those of the horizontal type. However, the machines of the vertical type are accompanied by some serious problems which give rise to difficulty in attaining satisfactory operation.

-In the vertical drying machine, the upper part of the drying chamber tends to be excessively heated by the heat generated in the chamber, and a heated mixture of air and solvent in the chamber tend to leak through the upper part of the drying chamber. These tendencies usually result in adhesion or sticking onto the guide roller of the treating medium applied on the strip material, and this often leads to damage to the material being treated.

Thus, the feed speed of the material to be subjected to drying operation is usually limited in the conventional machines by the sticking of the material to the guide roller at high speeds due to temperature rise in the guide roller.

Another problem in the maintenance of the machine is that, when the cap covering the guide roller is removed, leakage of the air and solvent occurs in great quantity from the drying chamber.

A simple method of cooling the guide roller from the inside has been resorted to for prevention of adhesion or sticking. However, this expedient is not satisfactory because the solvent vapor and moisture in the air tend to condensate on the surface of the guide roller. Furthermore, when the temperature of the material surface is higher than that of the guide roller, the treating medium on the material tends to be transferred onto the surface of the guide roller with resultant damage to the material being dried.

3,510,960 Patented May 12, 1970 SUMMARY OF THE INVENTION Accordingly, a main object of this invention is to provide a novel drying machine of the vertical type which is free of the above mentioned disadvantages.

Another object of this invention is to provide a novel drying machine wherein heat transfer from inside the drying chamber to the guide roller above the chamber and leakage of air and solvent from the drying chamber top are prevented.

Briefly stated, in accordance with a preferred embodiment of this invention, there is provided at least two vertically spaced sets of air curtain creating means which are located below the guide roller and above the top end of the vertical drying chamber. Each of the air curtain creating means includes air ejector nozzles so arranged that the upwardly and downwardly extending spans of the strip-like material running along the inverted U- shaped path are passed between opposing nozzles which direct air toward both surfaces of each span to. create air curtains or air stream layers for preventing ascent or leakage of the hot air and solvent in the drying chamber along the spans of the material to the guide roller. The space between the upper and lower sets of air curtain creating means receives the air ejected from the nozzles and serves to discharge the air to any desired place.

BRIEF DESCRIPTION OF THE DRAWING In the drawings:

FIG. 1 is a diagrammatic vertical section of an embodiment of this invention; and

FIG. 2 is an enlarged vertical section of a top assembly.

DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the drawing, the drying machine comprises a vertical housing 10 defining a drying chamber, which is divided by a vertical partition wall 11 into a pair of

sub-chambers

12 and 13 communicating with each other at their upper ends. These

subchambers

12 and 13 have therein heating means 14 which are arranged along the length of the sub-chambers and allow the strip S to be treated to pass therealong. The heating means 14 may be in the form of a series of pipes through which steam flows.

The sub-chamber 12 is provided with an inlet opening 15 for the strip S at the lower end thereof, and the subchamber 13 is provided with an outlet opening 16 for the strip S at the lower end thereof.

On the top of the housing 10, there is rigidly mounted a top assembly 20 having a removable cap 21. The top assembly 20 carries a rotatable roller 22 over which the strip S passes.

The strip 6 to be treated is supplied from a supply source (not shown) into a bath B of an appropriate treating medium which may, for example, be a coating material dissolved in a solvent. The strip which has been coated with the material of the bath B is fed through the inlet opening 15 into the sub-chamber 12 to be heated or dried by the heating means 14 and then passes over the roller 22 to be fed into the other sub-chamber 13. The strip is additionally subjected to heating or drying treatment when it passes through the sub-chamber 13, and is taken out from the chamber through the outlet opening 16.

The lowermost part of the subchamber 12 is communicatively connected to a cooling unit 30 through a conduit 31. The cooling unit 30 includes therein a cooling means 32 which may be a series of pipes through which cooling medium flows. The unit 30 is provided with a condensate collecting means 33.

The cooling unit 30 is communicatively connected through a conduit 35 to an air preheater unit 40 having therein heating means 41 which may, for example, be a series of pipes through which steam flows. The air preheater unit 40 is connected through a conduit 42 with the lowermost part of the sub-chamber 13. One of the

conduits

31, 35 and 42 may be provided therein with a fan 34 for forced circulation.

The vertical type drying machine as described above is known per se and operates as follows.

As the strip S, with the treating medium applied thereon in the bath B, is fed into the

drying chamber

12 and 13, it is subjected to heat generated from the heating means 14 with the resultant evaporation of the solvent from the surfaces of the strip. This evaporation causes the strip to be dried. The evaporated solvent in the drying chamber is drawn by the fan 34 through the conduit 31 into the cooling unit 30 and is condensed on the cooling means 32, thus flowing down to the condensate collecting means 33 to be taken out therefrom.

The fan 34 also draws heated air in the drying chamber. The air is cooled by the cooling means 32 and fed through the conduit 35 into the air preheater unit 40 to be preheated thereby. The preheated air from the unit 40 flows into the sub-chamber 13 and passes upwardly along the strip being fed in counter-current flow relative to the latter to be again drawn to the fan 34 through the sub-chamber 12. In the course of flowing along the strip in countercurrent flow thereto, the air promotes the evaporation of the solvent on the surfaces of the strip passing through the drying chamber.

The novel features of this invention reside in the provision of means including at least two sets of air curtain devices.

In accordance with the embodiment shown in the drawing, the top assembly includes a housing 50' in which are contained two sets of air-curtain devices.

The first or upper set of air-curtain devices comprises a pair of nozzle mounting members 51a and 51b rigidly secured on the inner wall of the housing 50 and a central nozzle mounting member 510 rigidly secured to the housing 50. These mounting members 51a, 51b and 51c extend in parallel spaced apart relationship to each other and carry air ejection nozzles.

The mounting members 51a and 51b rigidly carry

air nozzles

52a and 52b, and the central mounting member 510 rigidly carries on both sides air nozzles 520. The opposing pairs of

nozzles

52a, 52c and 52b, 52c respectively form gaps therebetween through which the upward and downward spans of the strip pass. The pair of nozzles 52a and 520 are on the same horizontal level and eject air streams toward each other onto the adjacent surfaces of the running strip, thus forming a kind of air curtain extending transversely to the running direction of the strip. The relation between the other pair of nozzles 52b and 520 are identical with that between

nozzles

52a and 52c, the upwardly run traveling span of the strip passing between the nozzles 52b and 520.

The second or lower set of air-curtain devices is identical with the first or upper set and therefore will not be explained in detail.

The upper set of air-curtain devices is disposed between

horizontal plates

55 and 56 having openings for the spans of the strips, and the lower set of air-curtain devices is disposed between

horizontal plates

57 and 58.

Between the upper and lower sets of the air-curtain devices, there is formed an intermediate space 60 which is in communication with the internal spaces of both the upper and lower sets of air-curtain devices. The space 60 is connected with an air discharge conduit 61 having a control valve 62.

A space 66 below the lower set of air-curtain devices is in communication with the drying chamber through openings 63 allowing the passage of the spans of the strip and also in communication with the internal space of the lower set of air-curtain devices. The space 66 is con- 4 nected With a discharge conduit 64 having a control valve 65.

In this type of the drying machine, it is desirable that the circulating air in the machine be prevented from flowing out of the machine. When the circulating air escapes, the drying efliciency of the machine and the rate of recovery of the solvent will naturally be decreased. The escape of the circulating air will also cause pollution of the atmosphere. In the vertical type drying machine, leakage of the internal fluid is most likely to occur in the upper part of the drying chamber because the pressure difference between the atmosphere and the internal air becomes the greatest at the uppermost part of the drying ghamber due to the internal heat generated in the cham- This difficulty can be eliminated with the air curtain devices of this invention.

In the course of the drying operation, the hottest air in the drying

chambers

12 and 13 gathers in the uppermost part thereof. Such air may, if desired, be exhausted to the outside remote from the machine through the conduit or chimney 64, and the exhaust may be stopped by closing the valve 65.

Under the closed condition of the control valve 65, the mixture of the air and solvent in the uppermost part of the drying chamber tends to ascend through the lower set of the air curtain devices. However, most of this mixture cannot pass through the air curtains or air stream layers, whereas these curtains or layers permit the strip to freely pass therethrough.

A small part of the mixture of the air and solvent, however, fiows into the space 60 with the injected air of the nozzles. This part of the mixture is further resisted by the air curtains or air streams created in the upper set of the air curtain devices and cannot ascend furthermore. Thus, it will be noted that the hot mixture of air and solvent can in no way fiow along the running strip into the internal space directly below the removable cap 21. The small part of the mixture which flows into the space 60 may be exhausted through the conduit or chimney 61 to a place remote from the machine.

Since the space 60 is always filled with cool air which has just been ejected from the lower set of the air curtain devices and the cool air is exhausted to carry off the heat of the hot mixtures which pass through the air curtains of the lower sets, almost no heat from the drying cham* ber reaches the roller 22 of the top assembly. It will be noted that the maintenance of the roller 22 in a cool condition and the prevention of leakage of the mixture to the roller 22 make it possible to prevent adhesion or sticking of the treating medium to the roller.

Because the pressure in the space surrounding the roller 22 is maintained substantially the same as that in the drying chamber in the closed condition of the cap 21, the ejection of air from the nozzles of the air curtain devices need not be very strong.

In the space surrounding the roller 22, there may be provided an air ejection device 70 which directs cool air onto the surface of the strip passing through the space. When such a device 70 is additionally provided, the prevention of leakage of the mixture of air and solvent from the drying chamber will be more effective because the air ejected from the device 70 flows into the space 60 so as to further restrain the leakage of the mixture toward the roller 22. The rate of exhaust through the conduit or chimney '61 can be appropriately adjusted by the control valve 62. When the valve 62 is set to a position in which the amount of air exhausted from the top assembly 20 is equal to that introduced into the assembly, the optimum condition is obtained.

Such a condition can also be attained by connecting the conduit 61 to the conduit 64 so as to form a closed circuit for the air. This procedure is advantageous because the closed circuit of air flow shuts out outside dust and prevents clogging of the air-curtain nozzles and because the closed circuit makes it possible to cool the air exhausted from the conduit 61 before it is again supplied to the conduit 64, for the purpose of maintaining constant operating condition. On the other hand, this procedure has the drawback of requiring removal of the solvent intermixed with the exhaust air before the air is again returned to the conduit 64.

Since the downward span of the strip coming from the roller 22 is in a cooled condition and the upward run of the strip coming from the drying chamber is in a hot condition, it is desirable that the air-curtain devices associated with the downward traveling span eject heated air to warm the span and that those associated with the upward traveling span eject cooled air to cool the run.

Furthermore, it is preferred that the lower set of the air-curtain devices supplies appropriately heated air to prevent condensation of the solvent in the drying chamber onto the air-curtain nozzles exposed to the chamber and to prevent condensed solvent on the nozzles from being splashed onto the strip by the ejection force of the air.

In the embodiment shown, the air ejected from the lower set of air curtain devices is supplied into the intermediate space 60. However, the air may be supplied into the lower space 62 so as to be exhausted through the conduit 64.

It is preferred that the nozzles be located as close as possible to the surfaces of the strip. However, it is important that the nozzles do not contact the strip.

When it is necessary to remove the cap 21, the control valve 65 is fully opened to direct the ejected air from the lower set of air curtain devices into the chamber 63. This effectively prevents the mixtures in the drying chamber from leaking in the upward direction.

Although this invention has been described with reference to a particular embodiment, it should be understood that this invention can be embodied in a form other than that described in the foregoing without departing the spirit of this invention.

What I claim is:

1. In a drying machine including a vertical drying chamber, a guide roller for a strip material to be treated provided at the top of said chamber, and means for passing the strip material through the interior of said chamber along an inverted U-shaped path passing over said guide roller, said material within the chamber assuming an inverted U by configuration with upwardly and downwardly traveling spans, the combination therewith of at least two vertically spaced sets of air curtain creating means positioned below said roller and above the top end of said drying chamber, each of said air curtain creating means including air ejector nozzle means so arranged that the lit) upwardly and downwardly traveling spans of the material are passed between the nozzles, which direct air toward both surfaces of each span to create air curtains for preventing ascent of hot fluid in the drying chamber along the spans of the material to said guide roller, the space between said sets of air curtain creating means serving to exhaust the air ejected from the nozzle of both sets.

2. The combination as claimed in claim 1, wherein a space is provided below the lower set of air curtain creating means and serves to exhaust the air ejected from the nozzles of the lower set.

3. The combination as claimed in claim 1, wherein said space between the vertically spaced sets of air curtain creating means is connected to a conduit having therein a control valve.

4. The combination as claimed in claim 2, wherein said space below the lower set of air curtain creating means is connected to a conduit having a control valve.

5. The combination as claimed in claim 2, wherein exhaust fluid from said space between the sets of air curtain creating means is supplied into the space below the lower set of air curtain creating means.

6. The combination as claimed in claim 1, wherein said sets of air curtain creating means and said guide roller are assembled in a top assembly.

7. The combination as claimed in claim 6, wherein said top assembly has a removable cap.

8. The combination as claimed in claim 6, wherein said top assembly contains an additional air ejecting device.

9. The combination as claimed in claim 1, wh rein the vertical drying chamber is divided into a pair of subchambers by a vertical partition which permits communication between the sub-chambers at their upper ends, and material heating means are arranged in the chamber along the path of the material to be dried, and wherein the material is passed through a bath of a treating medium dissolved in a solvent before it is introduced into the drying chamber and solvent recovery means are connected to the drying chamber for condensing and recovering the evaporated solvent in said chamber.

References Cited UNITED STATES PATENTS 2,532,471 12/1950 Welder 685.4 2,621,504 12/1952 Spooner 685.4 3,222,895 12/1965 Sheppard 685.4 3,396,415 8/1968 Windhorst 34-l55 LLOYD L. KING, Primary Examiner