US3648383A - Sealing apparatus for transport of material between regions at different pressures - Google Patents

Abstract

A seal to permit the passage of material, such as a continuous web bearing a layer of coating composition, between two zones at different gas pressures comprises a narrow passageway in communication with the two zones, a plurality of transverse ribs spaced along the longitudinal extent of the passageway, and a plurality of spaced apertures located within the troughs between adjacent ribs and communicating with a vacuum manifold for withdrawing gas from the passageway to provide a progressive change in pressure from a value at the inlet to the passageway equivalent to the pressure in the zone from which material is being transported to a value at the outlet from the passageway equivalent to the pressure in the zone into which the material is being transported. In a preferred embodiment, the seal is comprised of a smooth arcuate plate and a curved castellated shoe positioned opposite and in close proximity to the plate to define a narrow arcuate passageway therebetween. The seal is especially useful in the vacuum drying of web material having a surface coating which is especially susceptible to damage, such as a web consisting of a support coated with one or more layers of photographic emulsion.

Description

United States Patent Saunders amas Mar, M, 1972 Primary ExaminerFrederick L. Matteson Assistant Examiner-Harry B. Ramey Attorney-Walter O. Hodsdon and Alfred P. Lorenzo [5 7 ABSTRACT A seal to permit the passage of material, such as a continuous web bearing a layer of coating composition, between two zones at different gas pressures comprises a narrow passageway in communication with the two zones, a plurality of transverse ribs spaced along the longitudinal extent of the passageway, and a plurality of spaced apertures located within the troughs between adjacent ribs and communicating with a vacuum manifold for withdrawing gas from the passageway to provide a progressive change in pressure from a value at the inlet to the passageway equivalent to the pressure in the zone from which material is being transported to a value at the outlet from the passageway equivalent to the pressure in the zone into which the material is being transported. in a preferred embodiment, the seal is comprised of a smooth arcuate plate and a curved castellated shoe positioned opposite and in close proximity to the plate to define a narrow arcuate passageway therebetween. The seal is especially useful in the vacuum drying of web material having a surface coating which is especially susceptible to damage, such as a web consisting of a support coated with one or more layers of'photographic emulsion.

7 Claims, 3 Drawing Figures PMENTEDMAR 14 I972 SHEET 1 0F 2 R0 GER Lv SAUNDERS INVENTOR.

PATENTEDHAR 14 I972 3, 6A8 883 SHEET 2 OF 2 ROGER L. SAUNDERS INVENTOR.

SEALING APPARATUS FOR TRANSPORT OF MATERIAL BETWEEN REGIONS AT DIFFERENT PRESSURES The present invention relates to seals for use between two zones at different pressures when transporting material between the two zones and to methods of providing such seals.

The seal of the present invention has the advantage that is of particular utility where it is desired to transport a material having a readily damageable coating between two zones at different gas pressures without damage to the coating and without substantial passage of gas between the two zones.

According to the present invention, there is provided a seal for use between two zones at different pressures when transporting material between the two zones, the seal comprising means defining a narrow passageway in communication with each of the two zones through which, in use, a material is transportable and means for progressively changing the gas pressure through the length of the passageway, when the seal is in use, from a value, at the inlet to the passageway, equivalent to the pressure in the zone from which the material is being transported to a value, at the outlet from the passageway, equivalent to the pressure in the zone into which the material is being transported.

In a preferred embodiment of the invention, the narrow passageway is defined by a surface, arranged to carry the material to be transported, and a shoe positioned opposite the surface; the show having a plurality of apertures extending therethrough which are connected to a means for transferring gas into or out of the passageway. Preferably, the shoe comprises a series of surface irregularities extending transversely of the passageway, respective apertures being located in troughs of the surface irregularities. The apertures and surface irregularities enable the pressure in the passageway to be changed progressively along its length. Conveniently, the surface arranged to carry the material is a polished plate formed of, for example stainless steel. The plate may be treated to reduce friction, for example, with polytetrafluoroethylene which may be applied in the form of an aerosol spray. Additionally, the plate may be cooled, for example, by the circulation of water at a relatively low temperature. In an alternative embodiment of the invention, the surface may be defined by a roller mounted for rotation in the direction in which the material is being transported.

Preferably, the seal also comprises means for preventing inflow of gas through the sides of the narrow passageway. For example, where the surface is a polished plate, gaskets, which may be made of rubber, can be provided along the sides of the passageway.

Advantageously, the surface irregularities of the shoe are in the form of castellations comprising upstanding ribs having the troughs therebetween. Preferably, each rib has a plurality of grooves extending longitudinally thereof.

The seal of the present invention is particularly useful where it is desired to transport a material from a zone at a first pressure to another zone at a second, lesser pressure. In this case, the means for transferring gas is in the form of one or more manifolds connected to a vacuum pump or respective pumps.

The narrow passageway should be of dimensions greater, but not substantially greater, than the material to be transported. For example, the point of closest approach of the shoe and the material to be transported may be of the order of 0.010 to 0.013 inch, although smaller or larger gaps may be used.

The seal of the present invention is particularly useful where the material is in the form of a web. In this case, the narrow passageway is preferably arcuate longitudinally so that the web may be maintained under slight tension. As described more fully hereinafter, the web material may be a photographic material comprising a support having coated thereon one or more hydrophilic colloid layers e.g., light sensitive silver halide emulsion layers. Other applications include the transfer of webs coated with liquids having high viscosity, of adhesively coated webs, and of webs coated with set, nonhydrophilic colloids.

According to the present invention, there is further provided an apparatus comprising a chamber defining a zone arranged to be maintained at a pressure different from ambient pressure, said chamber having an inlet and an outlet through each of which a material is transportable, and wherein at least the inlet is provided with a sea] as aforestated.

Preferably, the apparatus is a vacuum drying apparatus and the chamber is a low-pressure enclosure.

According to the present invention, there is also provided a method of transporting a material between two zones maintained at different pressures, wherein the fluid pressure acting on the material is progressively changed from a value equivalent to that of the zone from which the material is being transported to a value equivalent to that of the zone into which the material is being transported.

In a preferred embodiment of the invention, the material is transferred from a zone at a particular pressure, e.g., ambient atmospheric pressure, to a zone maintained at a lower pressure. This embodiment of the invention is particularly useful where it is desired to dry coated hydrophilic colloid layers, e.g., light sensitive silver halide emulsion layers. The hydrophilic colloid layers may have been previously chilled.

The invention will now be described further with reference to the accompanying drawings, in which:

FIG. 1 is a partial, schematic view of a seal according to the present invention taken along the line l-l of FIG. 3;

FIG. 2 is a schematic view of a vacuum drying apparatus incorporating a seal according to the present invention; and

FIG. 3 is a fragmentary view, to an enlarged scale, of part of the seal shown in FIG. 1.

In FIG. 1 there is shown aseal 10 which is mounted on a vacuum chamber llll by means of abacking plate 12. Theseal 10 comprises a polishedarcuate surface 13, formed, for example, of a stainless steel. Thesurface 13 is attached to thebacking plate 12 by means of bolts (not shown). Thesurface 13 is treated to reduce friction e.g., by polytetrafluoroethylene applied in the form of an aerosol spray, and is provided with a cooling means (not shown) e.g., means for circulating relatively low temperature water. A web M, for example, a coated photographic material, is arranged to be passed over thesurface 13 through aninlet 15 into the vacuum chamber II in the direction indicated by thearrow 16.

Theseal 10 further comprises ashoe 17 of substantially the same arcuate shape as thesurface 13 and] mounted closely adjacent thereto to define anarrow passageway 18. Theshow 17 comprises a series of transverse castellations comprising upstanding ribs 19 (some of which are not shown) interspersed bytroughs 20. The point of closest approach of the ribs and the web is preferably constant and of the order of 0.010 to 0.013 inch but smaller or larger gaps may be used.

Preferably, means are provided for sealing thenarrow passageway 18 along the sides thereof to prevent inflow of air therethrough. For example, gaskets (not shown), which may be made of rubber, can be provided along each side of thenarrow passageway 18. Within each of the troughs 20 a plurality ofapertures 21 are provided (See FIG. 3). In a preferred em bodiment, theribs 19 have a plurality oflengthwise grooves 25 therealong. Theapertures 21 extend radially of the arcuate shape of and through theshoe 17. A plurality of manifolds 24 (only one of which is shown) which each communicate withrespective troughs 20 are mounted externally of the shoe l7 and are connected to a vacuum pump (not shown). In the embodiment illustrated, the arcuate shape of thepassageway 18 enables the web M to be maintained under slight tension.

In FIG. 2 there is shown avacuum drying apparatus 22 comprising a vacuum chamber 11 upon which is mounted abacking plate 12. The vacuum chamber 11 comprises an inlet and anoutlet 23. Mounted externally of the chamber 1 1 at theinlet 15 is aseal 10 of the type shown in FIG. 1. Mounted externally of the chamber 11 at theoutlet 23 is a further seal (not shown) which may be in accordance with the present invention or may be a conventional seal, such as contacting rollers having wipers, as the coated material is by such time dry. Heating means 26 are provided in the chamber 11.

In FIG. 3 there is shown a part of theshoe 17, to an enlarged scale, wherein the construction of theribs 19,troughs 20,apertures 21 and also thelengthwise grooves 25 can be seen more clearly.

In operation, a material such as aweb 14 in the form of a chilled, undried photographic material coated with hydrophilic colloid layers is transported through theseal 10 and into the vacuum chamber 11.

The vacuum pump is energized and draws air through theapertures 21 from thenarrow passageway 18 defined by thesurface 13 and theshoe 17. Thus, the pressure within thenarrow passageway 18 is reduced progressively in the direction of travel of the material from the external pressure at the inlet to the seal, to a value, at the exit from the seal, which is preferably equivalent to the pressure inside the vacuum chamber 11. This is because the air travelling with the material through theseal 10 has to pass successively through a plurality of short, narrow passages defined between theribs 19 and thesurface 13 with wider passages defined by thetroughs 20 and thesurface 13 therebetween. The pressure profile within theseal 10 may be measured by pressure tappings and suitable pressure gauges or manometers. It may be necessary to control this pressure profile by adjusting the pumping speed of the vacuum pump or by altering the number ofapertures 21 inparticular troughs 20, through which air can be drawn, in order to avoid possible damage to the coating of the material. Alternatively, valve means (not shown) may be located between eachmanifold 24 and the pump to regulate the rate at which air is drawn through the respective manifolds. In the embodiment shown, theweb 14 is coated on one side only and the coated side faces theshoe 17.

In an alternative embodiment of the invention, thesurface 13 may be defined by a roller mounted for rotation in the direction in which the material is being transported. In this case, a further seal would be provided in the chamber 11 at the exit of the surface and at the sides of the roller.

A number of other parameters have to be taken into account when operating the seal in drying a photographic material, to avoid damage to coating of the material being transported. These are:

a. the seal length and the number and size of the castellations; b. gap thickness between the seal and the coating;

c. pressure difference between the inlet and exit of the seal;

(1. temperature of the arcuate surface;

e. the type of hydrophilic colloid used and concentration thereof;

f. the presence or absence of salts modifying the character of the colloid; and

g. treatment of the coated web, particularly, chilling thereof between the point at which it is coated and that at which it enters the seal.

The properties of the seal were investigated using a coating and setting unit. A -inch wide web moving at a speed of 5 feet per minute was coated with gelatin solution and chilled by contact with a water cooled metal plate for seconds. The set web was then exposed to room air for seconds and then passed into one or other of the two seals (a) and (b) described below. After passing through the seal into a low-pressure enclosure, the web was visually examined through a window. The seal and enclosure are shown in FIG. 2.

One or other of two seals (a) and (b) substantially as shown in FIG. 1 were used. The seals had the following dimensions:

Length of film path in seal 5" 15" Width ofseal 6" 6" Width of web 5" 5" No. of ribs I6 60 No. of manifolds 4 12 Length in direction of seal of ribs Va" 9/64" Length in direction of seal of troughs W 7/64" No. of holes pertrough l0 14 Size of holes M" 7/64" N0, oftroughs per vacuum connection 3 5 Height of ribs l6" k" EXAMPLE 1 Seal (a) Coating solution-5 percent gelatin containing black colloidal silver pigment Coating thickness0.002 inch Pressure in vacuum chamber-230 mm. Hg

Table I gives the pressure at each trough in the seal.

EXAMPLE 2 Seal (a) Coating solution-5 percent gelatin containing a black colloidal silver pigment Coating thickness0.004 inch Pressure in vacuum chamber 570 mm. Hg

Table I gives the pressure at each trough in the seal.

EXAMPLE 3 Seal (a) Coating solution7 percent gelatin containing a black colloidal silver pigment Coating thickness 0.002 inch I Pressure in vacuum chamber-230 mm. Hg

Table I gives the pressure at each trough in the seal.

EXAMPLE 4 Seal (a) Coating solution7 percent gelatin containing a black colloidal silver pigment Coating thickness-0.004 inch Pressure in vacuum chamber-380 mm. Hg

Table I gives the pressure at each trough in the seal.

EXAMPLE 5 Seal (b) Coating solution-4 percent gelatin solution containing colloidal silver pigment Coating thickness0.002 inch Pressure in vacuum chamber-8.4 mm. Hg

Table II gives the pressure at each trough in the seal.

EXAMPLE 6 Seal (b) Coating solutionS percent gelatin solution containing colloidal silver pigment Coating thickness-0.004 inch pressure in vacuum chamber-J3 mm. Hg

Table II gives the pressure at each trough in the seal.

EXAMPLE 7 Seal (b) Coating solution7 percent gelatin solution containing colloidal silver pigment Coating thickness0.004 inch Pressure in vacuum chamber-7.0 mm. Hg

Table II gives the pressure at each trough in the seal.

An unsuitable pressure profile within the seal will produce damage to a coated web because of excessive air movement within the seal.

By adopting nonoptimum pressure profiles, damage was caused to the coating. However, if under these circumstances the chilling and setting of the web was improved, the damage to the coating could be lessened or obviated. Hence, the limits obtained (i.e., of colloid concentration and coating thickness) are peculiar to the equipment used, and in no way represent the limits of the invention. Modifications to the seal or chill section should make it possible to convey weaker and thicker coatings.

TABLE 1 Pressures (mm. Hg) at various points along seal (a) for Examples 1 to 4 Example l 2 3 4 Colloid concentration 5% 5% 7% 7% Coating thickness 0.002" 0.004" 0.002" 0.004" Atmospheric pressure 760 760 760 760 Pressure at trough 2 665 760 740 730 Pressure at trough 3 630 760 730 710 Pressure at trough 4 605 760 726 695 Pressure at trough 6 750 636 650 Pressure at trough 7 400 745 600 630 Pressure at trough 8 400 740 580 615 Pressure at trough 9 420 735 570 580 Pressure attrough 10 340 730 530 550 Pressure at trough 11 290 720 500 500 Pressure attrough 13 300 690 460 500 Pressure attrough 14 290 670 395 470 Pressure at trough 265 640 290 430 Pressure in vacuum chamber 230 570 230 380 TABLE 11 Pressures (mm. Hg) at various points along seal (b) for Examples 5 to 7 Example 5 6 7 Colloid concentration 4% 5% 7% Coating thickness 0.002" 0.004" 0.004" Atmospheric pressure 757 747 753 Pressure at trough No. 6 686 694 Pressure at trough No. 7 674 684 Pressure at trough No. 8 658 674 648 Pressure at trough No.9 646 667 631 Pressure at trough No. 10 636 659 621 Pressure at trough No. 11 628 652 607 Pressure at trough No. 12 619 644 605 Pressure at trough No. 13 606 634 576 Pressure attrough No 14 590 624 559 Pressure at trough No. 15 576 614 539 Pressure at trough No. 16 559 600 517 Pressure at trough No. 17 545 588 494 Pressure at trough No. 18. 516 565 464 Pressure at trough No. 19 493 538 427 Pressure at trough No. 20 469 525 469 Pressure at trough No. 21 424 496 332 Pressure at trough No. 22 40] 487 295 Pressure at trough No.23 341 443 246 Pressure at trough Nov 24 295 419 250 Pressure at trough No. 25 279 412 240 Pressure at trough No, 26 270 354 199 Pressure at trough No.27 242 311 164 Pressure at trough No. 2B 219 288 150 Pressure at trough No.29 191 233 149 Pressure at trough No. 30 190 230 141 Pressure at trough No.31 H36 225 131 Pressure at trough No, 32 174 210 103 Pressure at trough No.33 I56 183 87 Pressure at trough No, 34 134 150 85 Pressure at trough No. 35 131 146 79 Pressure at trough No. 36 116 130 67 Pressure at trough No.37 93 101 54 Pressure at trough No. 3B 84 88 Pressure at trough No. 39 80 87 Pressure ut trough No.40 78 84 Pressure at trough No. 41 68 70 36 Pressure ut trough No. 42 60 60 31 Pressure at trough No. 43 54 54 27 Pressure at trough No. 44 51 52 26 Pressure at trough No. 45 50 50 25 Pressure at trough Nov 46 44 44 21 Pressure at trough No. 47 3B 40 18 Pressure at trough No. 48 37 35 16 Pressure at trough No. 49 36 33 16 Pressure at trough No. 50 36 34 15 Pressure at trough No. 51 33 31 14 Pressure at trough No. 52 30 29 14 Pressure at trough NO. 53 26 26 14 Pressure at trough No. 54 25 23 11 Pressure at trough No. 55 25 24 14 Pressure at trough No. 56 24 23 14 Pressure at trough No. 57 22 21 14 Pressure at trough No, 58l7 l7 13 Pressure at trough No. 59I6 16 13 Pressure at trough No. 60l4 l3 12 Pressure in vacuum chamber 84 7.3 7.0

It will be appreciated that webs wider than 5 inches can be transported through a seal according to the invention providing the mechanical strength of the seal is adequate to withstand the pressures involved.

If desired, the spacing between the coated layer and the seal can be varied beyond the limits used in the examples. However, larger spacings require more air removal capacity while smaller spacings require more precise control of web movement.

If it is desired to transport weaker colloid solutions, a shoe having more castellations and using a more gradual pressure profile may be used.

Modifications within the scope of the present invention are envisaged. For example, if a web coated on both sides was to be transported, a double seal in which a castellated shoe was mounted on both sides of the inlet to the vacuum chamber could be used. It would be necessary, however, for the narrow passageway to have a planar shape. In this way the coated web would make no physical contact with the seal.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.

1 claim:

1. Sealing apparatus for the passage of material between two zones at different gas pressures, comprising a continuous plate; a shoe mounted opposite said plate and narrowly spaced therefrom to form a continuous narrow passageway therebetween having an open inlet and outlet in communication with opposite ones of said zones for passage of said material between said zones, the surface of said shoe forming one surface of said passageway including a plurality of trans verse ribs which extend into said passageway and are spaced along the length thereof, said shoe provided with a plurality of apertures in communication with said passageway and located between adjacent ribs, and a vacuum manifold system in communication with said plurality of apertures for maintaining a pressure within said passageway which progressively changes from a pressure at the inlet to said passageway equivalent to the pressure in the zone from which the material enters to a pressure at the outlet of said passageway equivalent to the pressure in the Zone into which the material passes.

2. Apparatus as described in claim 1 wherein said plate is of an arcuate configuration and said shoe is curved to correspond to the configuration of said plate and thereby form an arcuate passageway.

3. Sealing apparatus for the passage of a continuous web between two zones at different gas pressures, comprising a smooth arcuate plate for slideably supporting said web,

a curved shoe mounted opposite said plate and narrowly spaced therefrom to form an arcuate passageway therebetween for passage of said web, said shoe having a plurality of transversely extending ribs spaced along its longitudinal extent and protruding into said passageway and a plurality of spaced apertures within each of the troughs between adjacent ribs communicating with said passageway, and

a vacuum manifold system communicating with said plurality of apertures for withdrawing gas from said passageway through said apertures.

4. Sealing apparatus for sealing a port within a wall to permit the passage of a continuous web therethrough while maintaining a different gas pressure on each side of said wall, comprising an arcuate plate mounted on said wall adjacent said port for slideably supporting said web and directing it through said port,

a curved shoe mounted opposite said plate and narrowly spaced therefrom to form an arcuate passageway therebetween for passage of said web, said shoe having a plurality of transversely extending ribs spaced along its longitudinal extent and protruding into said passageway and a plurality of spaced apertures within each of the troughs between adjacent ribs communicating with said passageway,

a manifold communicating with said apertures, and

a vacuum pump operatively connected to said manifold for withdrawing gas from said passageway via said apertures.

5. Apparatus as described in claim 4 including a backing plate to which said arcuate plate and said shoe are affixed for mounting on said wall.

6. Apparatus as described in claim 3 wherein the distance between said arcuate plate and said curved shoe is such that the point of closest approach of said web material to said ribs is from about 0.010 to about 0.0l 3 inch.

7. Apparatus as described in claim 3 wherein each of said ribs is provided with a plurality of longitudinally extending grooves in the surface of the rib directly opposite to said arcuate plate.

Claims (7)

1. Sealing apparatus for the passage of material between two zones at different gas pressures, comprising a continuous plate; a shoe mounted opposite said plate and narrowly spaced therefrom to form a continuous narrow passageway therebetween having an open inlet and outlet in communication with opposite ones of said zones for passage of said material between said zones, the surface of said shoe forming one surface of said passageway including a plurality of transverse ribs which extend into said passageway and are spaced along the length thereof, said shoe provided with a plurality of apertures in communication with said passageway and located between adjacent ribs, and a vacuum manifold system in communication with said plurality of apertures for maintaining a pressure within said passageway which progressively changes from a pressure at the inlet to said passageway equivalent to the pressure in the zone from which the material enters to a pressure at the outlet of said passageway equivalent to the pressure in the zone into which the material passes.

2. Apparatus as described in claim 1 wherein said plate is of an arcuate configuration and said shoe is curved to correspond to the configuration of said plate and thereby form an arcuate passageway.

3. Sealing apparatus for the passage of a continuous web betwEen two zones at different gas pressures, comprising a smooth arcuate plate for slideably supporting said web, a curved shoe mounted opposite said plate and narrowly spaced therefrom to form an arcuate passageway therebetween for passage of said web, said shoe having a plurality of transversely extending ribs spaced along its longitudinal extent and protruding into said passageway and a plurality of spaced apertures within each of the troughs between adjacent ribs communicating with said passageway, and a vacuum manifold system communicating with said plurality of apertures for withdrawing gas from said passageway through said apertures.

4. Sealing apparatus for sealing a port within a wall to permit the passage of a continuous web therethrough while maintaining a different gas pressure on each side of said wall, comprising an arcuate plate mounted on said wall adjacent said port for slideably supporting said web and directing it through said port, a curved shoe mounted opposite said plate and narrowly spaced therefrom to form an arcuate passageway therebetween for passage of said web, said shoe having a plurality of transversely extending ribs spaced along its longitudinal extent and protruding into said passageway and a plurality of spaced apertures within each of the troughs between adjacent ribs communicating with said passageway, a manifold communicating with said apertures, and a vacuum pump operatively connected to said manifold for withdrawing gas from said passageway via said apertures.

5. Apparatus as described in claim 4 including a backing plate to which said arcuate plate and said shoe are affixed for mounting on said wall.

6. Apparatus as described in claim 3 wherein the distance between said arcuate plate and said curved shoe is such that the point of closest approach of said web material to said ribs is from about 0.010 to about 0.013 inch.

7. Apparatus as described in claim 3 wherein each of said ribs is provided with a plurality of longitudinally extending grooves in the surface of the rib directly opposite to said arcuate plate.

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