Photographic sheet material liquid processing apparatus and process for constructing a sealing ring

The apparatus includes a path-defining roller (28) and a sealing roller (38, 39) in contact therewith to seal the path-defining roller from the housing of the apparatus. A sealing ring (82) surrounds one end of the sealing roller and is urged into contact with a sealing surface (68). The sealing ring, in its relaxed condition, is undersized with respect to the sealing roller and when mounted on the sealing roller exhibits a flat face (96) to the sealing surface. The performance of the sealing is predicable and reliable.

DESCRIPTION 
1. Field of the Invention 
The present invention relates to an apparatus for the wet processing of 
photographic sheet material, such as X-ray film, pre-sensitised plates, 
graphic art film and paper, and offset plates. 
2. Background of Invention 
As a rule, a processing apparatus for photographic sheet material comprises 
several vessels each of which contains a treatment liquid, such as a 
developer, a fixer and a rinse liquid. As used herein, the term sheet 
material includes not only photographic material in the form of cut 
sheets, but also in the form of a web unwound from a roll. The sheet 
material to be processed is transported through these vessels in turn, by 
transport means such as one or more pairs of drive rollers, and thereafter 
optionally to a drying unit. 
A photographic sheet material liquid processing apparatus has been proposed 
in European patent application EPA 95203465.0 (filed Dec. 13, 1995) 
comprising a housing in which a path-defining roller is mounted, biased 
towards a reaction surface (usually another path-defining roller) to form 
a nip there-between through which a sheet material path extends. A sealing 
roller is positioned in contact with the path-defining roller along the 
length thereof to seal the path-defining roller from the housing. By the 
use of a sealing roller in place of the more common stationary sealing 
member, the torque which needs to be applied to the path-defining roller 
can be significantly reduced. This reduces the power needed by the 
processor, reduces wear on the path-defining roller, reduces the 
mechanical deformation thereof and thereby extends the expected life time. 
This construction also improves the control of pressure distribution over 
the sheet material. 
The ends of the sealing roller need to be in contact in a leak-free manner 
with a sealing surface, such as an end plate secured to, or located in a 
fixed position relative to, the housing of the apparatus. It is important 
that the sealing rollers are retained in these end plates in a leak-free 
manner. Sealing rings formed for example of PTFE, are therefore provided, 
one surrounding each end of the sealing roller and urged into contact with 
sealing surfaces perpendicular to the sealing roller axis. It is also 
important that the sealing rings are so constructed as to compensate for 
the wear thereof. 
This previously proposed construction suffers from the disadvantage of 
relying on the creeping effect of the sealing ring material under 
pressure. It is found that creeping is not a continuous flow, due to 
internal mechanical resistances. This makes the performance of the sealing 
unpredictable and unreliable. 
OBJECTS OF INVENTION 
It is object of the present invention to overcome the aforesaid 
disadvantage in a simple and cost effective manner. 
SUMMARY OF THE INVENTION 
We have discovered that this objective, and other useful advantages, can be 
achieved when the sealing ring has a configuration which, in its relaxed 
condition, is undersized with respect to the sealing roller and when 
mounted on the sealing roller exhibits a flat face in the plane 
perpendicular to the sealing roller axis. 
Thus, according to a first aspect of the invention, there is provided a 
photographic sheet material liquid processing apparatus comprising a 
housing, a path-defining roller mounted in the housing and biased towards 
a reaction surface to form a nip there-between through which a sheet 
material path extends, a sealing roller in contact with the path-defining 
roller along the length thereof to seal the path-defining roller from the 
housing, and a sealing ring which surrounds one end of the sealing roller 
and is urged into contact with a sealing surface, characterised in that 
the sealing ring has a configuration which, in its relaxed condition, is 
undersized with respect to the sealing roller and when mounted on the 
sealing roller exhibits a flat face in the plane perpendicular to the 
sealing roller axis. 
A line contact between the sealing rollers and the sealing rings is 
preferred to a surface-to-surface contact. In one embodiment, the sealing 
ring which surrounds the end of the sealing roller is urged into 
line-to-surface sealing engagement with the surface of the sealing roller 
by a spring. It is possible that line contact between the sealing roller 
and the sealing ring need not extend circumferentially completely around 
the sealing roller, and indeed there would be an advantage in this line 
contact extending only part way around the sealing roller, but on the 
liquid side thereof. This construction makes the tolerances to which the 
sealing roller and the sealing rings are constructed less critical. 
Preferably, the sealing ring has a composite structure, comprising a spring 
embedded in elastomeric material. The spring may be formed of a metal ring 
structure based on Cr--Ni wire or an open metal structure based upon a 
Cr--Ni thin plate. The sealing ring may have a composite structure 
comprising at least two discrete regions, namely a sealing roller 
contacting region formed of a material of relatively low friction, that is 
lower than that of the other region, and a sealing surface contacting 
region formed of a material of relatively high elasticity, that is higher 
than that of the other region. This construction has the advantage that 
two different functions are complied with, that is firstly the sealing 
against the sealing roller using the classical sealing characteristics of 
pressure against a contact surface, and secondly the sealing face of the 
sealing ring, perpendicular to the sealing roller axis, being flat. In 
such a manner this sealing surface can be brought into the same surface as 
the sealing holder. This is a necessary characteristic for the sealing 
ring, because this common surface also acts as a sealing surface for the 
top end of the path-defining roller. 
The material of relatively low friction may be selected from fluorinated 
polymers such as PTFE, oxymethylene polymers, acrylic polymers and ether 
sulphone polymers. In particular, we prefer to use a material for this 
region of the sealing ring which has good "creeping" characteristics to 
compensate for the wear under spring pressure, such as sintered PTFE. 
The material of relatively high elasticity may be selected from 
ethylene/propylene/diene terpolymers (EPDM), silicone rubber, 
polyurethane, thermoplastic rubber such as Santoprene (Trade Mark for 
polypropylene/EPDM rubber), styrene-butyl rubber, nitrile-butyl rubber, 
PFA and Fluor-Latex (FLC) materials. 
The sealing surface may be constituted by an end plate fixed to the 
housing, through an aperture of which the sealing roller passes. 
According to a second aspect of the invention, there is provided a process 
for forming a sealing ring for use with a sealing roller in a photographic 
sheet material liquid processing apparatus, comprising forming a ring-like 
member which may be undersized with respect to the sealing roller and 
which includes a cut out portion opening onto an end of the ring-like 
member, forcing the ring-like member over a mandrel having a size 
substantiality equal to the size of the sealing roller, that is having a 
size which may be closer to the size of the sealing roller than to the 
relaxed size of the sealing ring, and filling the cut out portion with 
elastomeric material so as to provide a sealing ring with a flat end face. 
Where a spring is included in the sealing ring, this may be inserted while 
the sealing ring is in a deformed state positioned over the mandrel 
before, or while, the cut-out portions are being filled with elastomeric 
material. 
The sealing ring may be removed from the mandrel and then fitted onto one 
end of the sealing roller. Alternatively, the sealing roller itself may be 
used as the mandrel. 
After filling the cut out portion with the elastomeric material and while 
the ring-like member is positioned over the mandrel, the end of the 
ring-like member may be ground to provide the flat face. 
In a conventional processing apparatus the sheet material is transported 
along a generally horizontal feed path, the sheet material passing from 
one vessel to another usually via a circuitous feed path passing under the 
surface of each treatment liquid and over dividing walls between the 
vessels. However, processing machines having a substantially vertical 
orientation have also been proposed, in which a plurality of vessels are 
mounted one above the other, each vessel having an opening at the top 
acting as a sheet material inlet and an opening at the bottom acting as a 
sheet material outlet or vice versa. In the present context, the term 
"substantially vertical" is intended to mean that the sheet material moves 
along a path from the inlet to the outlet which is either exactly 
vertical, or which has a vertical component greater than any horizontal 
component. The use of a vertical orientation for the apparatus leads to a 
number of advantages. In particular the apparatus occupies only a fraction 
of the floor space which is occupied by a conventional horizontal 
arrangement. Furthermore, the sheet transport path in a vertically 
oriented apparatus may be substantially straight, in contrast to the 
circuitous feed path which is usual in a horizontally oriented apparatus. 
As a consequence of the straight path, the material sensitivity for 
scratches becomes independent of the stiffness and thickness of the 
material. The present invention can also be made use of in an apparatus of 
hybrid configuration, that is an apparatus having one or more vessels 
through which the sheet material passes along a generally vertical path, 
coupled to one or more vessels through which the sheet material passes 
along a generally horizontal path. In particular, a 
vertical-horizontal-vertical path may be employed, with an up-across-down 
or, more preferably, a down-across-up sheet material path direction. 
Although the bending of the sheet material in an apparatus of conventional 
horizontal configuration is seen as undesirable, this is less so where the 
sheet bending takes place under the surface of a liquid. 
While the present invention is applicable to apparatus with either a 
horizontal, vertical or hybrid orientation, it is particularly applicable 
to a vertical apparatus, because it is in such an apparatus that it is 
important to avoid, or at least minimise leakage of treatment liquid from 
one vessel to another and carry-over as the sheet material passes through 
the apparatus. 
The apparatus may comprise at least one treatment vessel having upper and 
lower openings, one of the openings constituting a sheet material inlet 
and the other of the openings constituting a sheet material outlet. A 
substantially vertical sheet material path through the vessel may thus be 
defined by the inlet and outlet and by the nip. 
The reaction surface towards which the path-defining roller is biased to 
define the nip will usually be the surface of another path-defining 
roller, or the reaction surface may be in the form of a belt or a fixed 
surface with a low friction coefficient. Where this general description 
refers to the use of two path-defining rollers, it is to be understood 
that the second path-defining roller may be replaced by any other reaction 
surface, such as those referred to above. 
The sealing roller may have a diameter less than that of the path-defining 
roller. For example, the sealing roller may have a diameter which is from 
one tenth to one third of the diameter of the path-defining roller, 
thereby enabling the torque which needs to be applied to be further 
reduced. The sealing roller preferably extends in a straight line parallel 
to the associated path-defining roller axis and preferably contacts the 
surface of the associated path-defining roller at a location which is 
between 45.degree. and 315.degree., most preferably between 80.degree. and 
100.degree. from the centre of the nip, on the fluid side. 
The sealing roller may be formed of a material having a coefficient of 
friction (as measured against stainless steel) of less than 0.3, 
preferably from 0.05 to 0.2, for example highly polished metals such as 
steel, especially Cr--Ni steel and Cr--Ni--Mo steel, a metal coated with 
Ni-PTFE (NIFLOR--Trade Mark), a polymer material such as PTFE (poly tetra 
fluoro ethylene), POM (polyoxymethylene), HDPE (high density 
polyethylene), UHMPE (ultra high molecular weight polyethylene), 
polyurethane, PA (polyamide), PBT (polybutyl terephthalate) and mixtures 
and composites thereof. 
In a preferred embodiment, the sealing roller is carried by a longitudinal 
bearing, secured within the vessel. The longitudinal bearing may have 
face-to-face contact with the sealing roller over at least two contact 
regions, which are located, for example, at from .+-.120.degree. to 
150.degree. relative to the line joining the centres of a path-defining 
roller and its associated sealing roller, such as .+-.135.degree. to that 
line. The width of contact between a sealing roller and its associated 
longitudinal bearing in each contact region is, for example, from 
20.degree. to 40.degree. of the circumference of the sealing roller, which 
in the case of a sealing roller having a diameter of 8 mm may be about 2 
mm per contact region. 
The surface of the sealing roller opposite to the path-defining roller may 
be in contact with one or more fixed sealing members carried in, or formed 
as part of, the longitudinal bearing. The fixed sealing member may, for 
example, be retained within a longitudinal groove formed in the 
longitudinal bearing. The fixed sealing member may have a symmetrical 
profile section but a non-symmetrical profile section is also possible, 
its shape and resilience taking into account the hydrostatic and 
hydrodynamic pressures in the vessel and the interacting forces with the 
sealing roller, allowing for the fact that the path-defining roller and 
the sealing roller may be adapted to rotate in both directions. 
The fixed sealing member which is carried in, or formed as part of, the 
longitudinal bearing preferably exerts a pressure on the sealing roller 
which is at least .rho.*g*h, most preferably at least 2.rho.*g*h, where 
.rho. is the density of the treatment liquid (typically up to 1200 
kg/m.sup.3), g is 9.8 m/s.sup.2 and h is the height of the treatment 
liquid above the sealing point. To reduce friction at this point, the 
contact surface between the fixed sealing member and the sealing roller is 
kept to a minimum. It is also desirable to establish a sealing pressure 
between the path-defining roller and the sealing roller. While this should 
preferably also exceed .rho.*g*h and most preferably 2 .rho.*g*h, the 
absolute force applied by the path-defining roller to the sealing roller 
should be greater than the absolute force exerted by the fixed sealing 
member on the sealing roller to ensure that the sealing roller touches the 
bearing surfaces of the longitudinal bearing. This enables the absolute 
force exerted by the sealing roller on the bearing surfaces to be reduced 
to a minimum thereby reducing the friction at this point. The pressure 
exerted by the path-defining roller on the sealing roller may be derived 
from the mounting of the sealing roller or simply from compression of the 
elastomeric material covering of the associated path-defining roller or 
from spring forces exerted on the path-defining roller. 
It is preferred that the end faces of the sealing roller and fixed sealing 
member extend beyond the end faces of the elastomeric part of the 
path-defining roller. In this way the sealing function is less dependant 
on tolerances and differential thermal expansion of these components and 
their thermal expansion relative to the path-defining roller, more 
precisely between the end faces of the path-defining roller. That is, it 
is preferred that the stationary sealing member is longer than the 
associated path-defining roller, and further that the contact surfaces of 
the longitudinal bearing with the sealing roller are shorter than the 
associated path-defining roller. 
Preferably, the path-defining roller comprises a core carrying an 
elastomeric material covering, although it is possible for the 
path-defining roller to be elastomeric throughout its cross-section. By 
the term "core" we mean an axially inner member, which is usually 
cylindrical and which is relatively rigid compared to the elastomeric 
material covering. The core may be solid or hollow. Usually, drive to the 
roller will be applied to the core. In a preferred embodiment of the 
invention, each of the ends of the elastomeric material covering are in 
sealing contact with a surface of the end plates. The surface of each end 
plate may be formed of, or coated with, a low friction material such as 
polished metal, or polytetrafluoroethylene. The elastomeric material may 
extend beyond the ends of the core, the sealing means being in contact 
with the end faces of the covering. The extension of the covering beyond 
the end of the core defines a space into which the elastomeric material of 
the covering may be deformed as a result of a sealing force between the 
covering and the end plate. Such an arrangement improves the sealing 
between the path-defining roller and the end plate. In a preferred 
embodiment of the invention, the roller comprises an inner layer of 
elastomeric material having a relatively low hardness, and an outer region 
of elastomeric material having a relatively high hardness positioned over 
the inner layer. Such a roller minimises carry-over between vessels 
without damage to the sheet material while being capable of successfully 
being used as a drive roller. Such a path-defining roller exhibits good 
stability against treatment liquids and has good processing qualities. 
It is a preferred feature of the present invention that the end faces of 
one path-defining roller lie in substantially the same planes as the end 
faces of the other path-defining roller. By the term "end face" we mean 
the face at the end of the roller, adjacent the outer surface thereof. 
Thus, where the roller comprises a core provided with an elastomeric 
material, the term "end face" as used herein means the end face of the 
elastomeric material covering. In this embodiment, an end face of one 
roller lies in exactly the same plane as an end face of the other roller, 
or in such a closely adjacent plane that an effective seal can be made 
between the end faces and the end plate or other stationary body fixed to 
the housing of the apparatus, taking into account any resilience in the 
material of which the roller and the end plate may be formed. As a 
consequence of this requirement, the elastomeric part of the path-defining 
rollers are substantially equal in length. 
The end plates are preferably biased against the end faces of the 
path-defining rollers with a force of from 2 to 500 g/cm of contact 
between the end plate and the end face of the roller, measured on the 
surface of the roller. The pressure between the end face of the 
path-defining roller and the end plate should also be at least .rho.*g*h. 
We prefer that the pressure between the end face of the path-defining 
roller and the end plate should be at least 2.rho.*g*h. Thus, the end 
plates may be urged against the end faces of the path-defining rollers by 
springs so shaped to ensure the desired location of the contact line 
between the end plates and the end faces of the rollers. Alternatively the 
elastomeric material covering of the path-defining rollers is somewhat 
oversized, the necessary spring force then being derived from the 
elasticity of the elastomeric material itself. 
One or both of the path-defining rollers may constitute a drive roller for 
driving the sheet material along the sheet material path. Alternatively, 
the path-defining rollers may be freely rotating, alternative drive means 
being provided to drive the photographic sheet material through the 
apparatus. 
The path-defining rollers may be biased together by a variety of methods, 
for example by making use of the intrinsic elasticity of the elastomeric 
material, by the use of fixed path-defining roller bearings. 
Alternatively, use may be made of resilient means such as springs which 
act on the ends of the path-defining roller shafts. The springs may be 
replaced by alternative equivalent compression means, such as e.g. a 
pneumatic or a hydraulic cylinder. 
Each vessel of the apparatus according to the invention may be of modular 
construction and be provided with means to enable the vessel to be mounted 
directly above or below an identical or similar other vessel. 
Alternatively, the apparatus may take an integral form or semi-integral 
form. By the term "semi-integral form" we intend to include an apparatus 
which is divided by a substantially vertical plane passing through all the 
vessels in the apparatus, particularly the plane of the sheet material 
path, enabling the apparatus to be opened-up for servicing purposes, in 
particular to enable easy access to the path-defining rollers. 
The apparatus according to the invention may include a substantially closed 
connection between adjacent vessels. 
Each vessel of the apparatus may comprise a housing having an upper housing 
part and a lower housing part, the upper housing part being so shaped in 
relation to the lower housing part of the next higher vessel as to provide 
the substantially closed connection between adjacent vessels. For example, 
the upper and lower housing wall parts may be provided with flanges, means 
being provided to secure the flange of the upper housing wall part with 
the flange of the lower housing wall part of the next higher vessel 
thereby to provide the substantially closed connection. Optionally, a 
gasket may be positioned between the vessels to improve the reliability of 
this connection. 
The top-most liquid-containing vessel of the apparatus is preferably 
provided with closure means for reducing the evaporation, oxidation and 
carbonisation of treatment liquid therefrom (and any other undesirable 
exchange between the treatment liquid and the environment). 
The upper part of the housing of each vessel (optionally other than the 
top-most) is preferably so shaped as to define a leakage tray so 
positioned that any treatment liquid which passes, for example, through 
the path-defining roller nip of the next higher vessel drips from the 
path-defining rollers of that vessel and falls into the leakage tray, for 
collection and recirculation as desired. 
By the use of a vertical configuration, the cross-section of the vessel can 
be low, such as less than 3 times the path-defining roller diameter. The 
volume of the vessel can therefore be low. Indeed, for a given sheet 
material path length, the volume of one vessel of a vertical processing 
apparatus can be many times smaller than the volume of an equivalent 
treatment bath in a horizontal processing apparatus. This has advantages 
in terms of the volume of treatment liquids used and the efficiency of 
their interaction with the sheet material. 
Nevertheless, one or more of the vessels of the apparatus may include 
additional features if desired. Cleaning means may be provided for acting 
upon the path-defining rollers to remove debris therefrom, as described in 
European patent application EP 93202862 (Agfa-Gevaert NV), filed Oct. 11, 
1993. Additional path-defining rollers, such as a path-defining roller 
pair or staggered path-defining rollers may be provided for transporting 
the sheet material through the apparatus, and these path-defining rollers 
will normally be driven path-defining rollers. Additional roller pairs may 
be provided for breaking the laminar fluid at the surface of the sheet 
material as it passes through the apparatus, and these rollers may be 
driven rollers or freely rotating rollers. Even when additional roller 
pairs are present, the path-defining rollers will usually constitute the 
lower roller pair, serving to close the lower opening of the vessel. Spray 
means may be provided for applying treatment liquid to the sheet material. 
Guide means may be included for guiding the passage of the sheet material 
through the apparatus. Heating means may be provided in one or more 
vessels so that the vessel becomes a sheet material drying unit, rather 
than a wet treatment unit. While liquid pumping, heating, cooling and 
filtering facilities will normally be provided outside the vessels, it is 
possible for some elements of these features to be included in the vessels 
themselves. Any combination of these additional features is also possible. 
In one embodiment of the invention, one or more of the vessels includes at 
least one passage through the housing thereof to constitute an inlet 
and/or outlet for treatment liquid into and/or from the associated vessel. 
One or more vessels may not contain processing liquid, these vessels 
providing a dead space where diffusion reactions can occur on the sheet 
material as it passes there-through. 
As the sheet material leaves a given liquid treatment vessel it is 
necessary to remove any liquid carried on the sheet material as 
efficiently as possible, to reduce edge effects which arise from 
non-homogeneous chemistry on the sheet material after squeegeeing. To do 
this job properly, the path-defining rollers must exert a sufficient and 
homogeneous pressure over the whole width of the sheet material. Also, to 
reduce edge effects, it is desirable that the opposite path-defining 
roller surfaces are in contact with each other beyond the edges of the 
sheet material. To put this problem in context, path-defining rollers used 
in conventional processing apparatus for example having a length of 400 mm 
to 2000 mm or more and a diameter of from 20 to 60 mm. The sheet material 
typically has a width of from a few millimetres up to 2 m and a thickness 
of 0.05 mm to 0.5 mm. In view of the nature of elastomeric material, it is 
in fact impossible to totally eliminate any gap between the path-defining 
roller surfaces at the edges of the sheet material as it passes through 
the nip. It is desirable that the path-defining roller surfaces be in 
contact with each other within as short a distance as possible from the 
edges of the sheet material i.e. that the size of the leak zone should be 
minimised. It is important however that the force between the 
path-defining rollers is sufficient to prevent leakage when no sheet 
material is passing through. However, the force must not be so high as to 
risk physical damage to the sheet material as it passes through the nip. 
The objective of a minimum leak zone referred to above can be achieved if 
the ratio of the diameter of the path-defining roller to its length is 
above a critical limit. 
To enable this objective to be achieved, the ratio of the diameter of the 
path-defining roller to its length should be above a critical limit. In 
particular, at least one of the path-defining rollers, and preferably each 
path-defining roller, comprises a rigid core carrying a covering of 
elastomeric material, the ratio (.phi./L) of the maximum diameter (.phi.) 
of the elastomeric material covering to the length (L) thereof being at 
least 0.012, most preferably between 0.03 and 0.06. Preferably both 
path-defining rollers conform to this requirement, although it is possible 
that the diameters (.phi.), and therefore the ratios (.phi./L), of the two 
path-defining rollers need not be identical. 
The elastomeric material covering preferably has a thickness of between 1 
mm and 30 mm. The elastomeric material may be selected from 
ethylene/propylene/diene terpolymers (EPDM), silicone rubber, 
polyurethane, thermoplastic rubber such as Santoprene (Trade Mark for 
polypropylene/EPDM rubber), styrene-butyl rubber, nitrile-butyl rubber, 
PFA and Fluor-Latex (FLC) materials. The hardness of the elastomeric 
material may be between 15 Shore (A) and 90 Shore (A), as measured on the 
roller surface. Where the elastomeric material comprises an inner layer of 
relatively low hardness and an outer layer of relatively high hardness, 
the inner layer should have a hardness of less than 50 Shore A, while the 
outer layer should have a hardness of more than 25 Shore A. 
In one embodiment, the diameter (.phi.) of the elastomeric material 
covering is constant along the length of the path-defining roller. 
Alternatively the path-defining roller may have a radial dimension profile 
which varies along the length thereof. In the latter case, the diameter 
(.phi.) in the expression .phi./L is the maximum diameter. Alternatively 
or additionally, the diameter of the core varies along the length thereof. 
Ideally, the radial dimension profile of such a path-defining roller is 
such in relation to the force applied by the path-defining roller to sheet 
material passing through the nip as to be substantially even over the 
width thereof. 
Preferably, the core has a flexural E-modulus of between 50 GPa and 300 
GPa. Suitable materials for the rigid core include metals, such as 
stainless steel, non-ferrous alloys, titanium, aluminium or a composite 
thereof. In one embodiment of the invention, the core is hollow. 
Alternatively the core may be solid. 
DETAILED DESCRIPTION OF THE INVENTION

Although only one specific embodiment of a treatment vessel according to 
the invention is shown in the Figures, the invention is not restricted 
thereto. The apparatus for the wet processing of photographic sheet 
material such as X-ray film as shown in the Figures comprises a plurality 
of treatment vessels mounted one above another. These vessels may be 
arranged to provide a sequence of steps in the processing of sheet 
photographic material, such as developing, fixing and rinsing. The vessels 
may be of a modular structure as shown or may be part of an integral 
apparatus. 
As shown in FIG. 1, each vessel 12 comprises a housing 14 which is of 
generally rectangular cross-section and is so shaped as to provide an 
upper part 15 having an upper opening 17 and a lower part 16 having a 
lower opening 18. The upper opening 17 constitutes a sheet material inlet 
and the lower opening 18 constitutes a sheet material outlet. The inlet 
and outlet define there-between a substantially vertical sheet material 
path 20 through the vessel 12, the sheet material 22 moving in a downwards 
direction as indicated by the arrow A. Each vessel 12 may contain 
treatment liquid 24, a passage 26 in the housing 14 being provided as an 
inlet for the treatment liquid 24. 
The lower opening 18 is closed by a pair of rotatable path-defining rollers 
28, 30 carried in the apparatus. Each path-defining roller 28, 30 is of 
the squeegee type comprising a stainless steel hollow core 32 carrying an 
elastomeric covering 34. The core 32 is in cylindrical form having 
constant internal and external diameters along the length thereof. The 
path-defining rollers 28, 30 are of identical length biased towards each 
other with a force sufficient to effect a liquid tight seal but without 
causing damage to the photographic sheet material 22 as it passes 
there-between. The line of contact between the path-defining rollers 28, 
30 defines a nip 36. The nip 36 has a length which extends beyond the 
limits of the lower opening 18. The sheet material preferably has a width 
which is at least 10 mm smaller than the length of the nip 36, so as to 
enable a spacing of at least 5 mm between the edges of the sheet and the 
adjacent limit of the nip, thereby to minimise leakage. The path-defining 
rollers 28, 30 are coupled to drive means (not shown) so as to constitute 
drive rollers for driving the sheet material 22 along the sheet material 
path 20. 
Each path-defining roller 28, 30 is in sealing contact along its length, 
with a respective rotatable sealing roller 38, 39 formed for example of 
hardened or PTFE-coated metal carried by a longitudinal bearing 40, 
formed, for example, of high density polyethylene. As can be seen in FIG. 
4, the longitudinal bearing 40 is in face-to-face contact with the sealing 
roller over two contact regions 80, which are positioned one on either 
side of a groove 81 extending along the length of the longitudinal bearing 
40, the contact regions 80 being located at an angle .alpha. of 
.+-.135.degree. relative to the line joining the centres of a 
path-defining roller 28 and the sealing roller 38. The longitudinal 
bearing 40 is secured to the housing 14 of the vessel 12, the treatment 
liquid 24 being retained in the vessel 12 by the path-defining rollers 28, 
30 and the sealing rollers 38, 39. The sealing roller 38 contacts the 
surface 71 of the first path-defining roller 28 at a location which, in 
this particular embodiment, is about 90.degree. from the centre of the nip 
36 on the fluid side, that is from the plane joining the axes of rotation 
of the path-defining rollers 28, 30. The benefit of this arrangement is 
that the sealing force on the path-defining roller does not influence the 
bias forces between the rollers, or only influences these forces to a 
limited extent. 
Where the apparatus is designed to operate in the opposite direction, the 
active forces on the path-defining roller versus the nip may be modified 
to take account, in particular, of the consequential differences in the 
reaction forces of the sealing roller on the path-defining roller in such 
a way that the forces on the sheet material are kept constant. 
The upper and lower housing parts 15, 16 are provided with flanges 19, 21 
respectively to enable the vessel 12 to be mounted directly above or below 
an identical or similar other vessel 12', 12", as partly indicated in 
broken lines in FIG. 1. The upper housing part 15 is so shaped in relation 
to the lower housing part 16 as to provide a substantially closed 
connection between adjacent vessels. Thus, treatment liquid from vessel 12 
is prevented from falling into the lower vessel 12" by the path-defining 
rollers 28, 30 and sealing rollers 38, 39, while vapours from the lower 
vessel 12" are prevented from entering the vessel 12 or escaping into the 
environment. This construction has the advantage that the treatment liquid 
in one vessel 12 is not contaminated by contents of the adjacent vessels 
and that by virtue of the treatment liquids being in a closed system 
evaporation, oxidation and carbonisation thereof is significantly reduced. 
The upper part 15 of the housing 14 is so shaped as to define a leakage 
tray 42. Any treatment liquid which may pass through the roller nip of the 
next higher vessel 12', in particular as the sheet material 22 passes 
therethrough, drips from the path-defining rollers of that vessel and 
falls into the leakage tray 42 from where it may be recovered and 
recirculated as desired. The distance H between the surface 25 of the 
liquid 24 and the nip of the path-defining rollers of the next upper 
vessel 12' is as low as possible. 
The construction of path-defining roller 28 is shown in more detail in 
FIGS. 2, 3 and 4. The construction of path-defining roller 30 is similar. 
The roller 28 comprises a hollow core 32 of stainless steel, having a 
constant outside diameter of 25 mm and an internal diameter of 19 mm. The 
stainless steel core 32 has a flexural E-modulus of 210 GPa. The core 32 
is provided with a covering 34 of EPDM rubber, an elastomer having a 
hardness of 30 Shore (A). The elastomeric covering 34 has a thickness 
varying from 7 mm and the roller ends to 7.5 mm at the roller centre. The 
path-defining roller 28 has a length of 750 mm and a maximum diameter of 
40 mm. The maximum .phi./L ratio is therefore approximately 0.053. The 
core 32 is welded to a roller shaft 54 which extends axially out of the 
roller, the free end of the roller shaft 54 being retained in a bearing 46 
or coupled to a drive wheel (not shown) to provide drive to the roller. 
The path-defining roller 28 is in contact with the sealing roller 38 along 
the length thereof. Each end of the sealing roller 38 extends into an 
aperture 70 formed in an end plate 62 carried on the housing 14 of the 
apparatus. The aperture 70 is open-sided towards the top as viewed in the 
Figures. 
The upper surface of the sealing roller 38 is in contact with a fixed 
sealing member 75 in strip form, which is a pressure fit in the groove 81 
of the longitudinal bearing 40 or alternatively is secured therein by 
means of a water- and chemical-proof adhesive. The end of the longitudinal 
bearing is secured to a fixed transverse sealing 85, which is provided 
with thermal expansion holes. 
The sealing roller 38 extends beyond the end face of the covering 34 of the 
path-defining roller 28, the end face being vulcanised to a roller end 
covering 68, formed for example of EPDM containing 30% PTFE. In this way 
the sealing function is less dependant on tolerances and differential 
thermal expansion of these components and their thermal expansion relative 
to the path-defining roller, more precisely between the end faces of the 
path-defining roller. Further, the contact surfaces of the longitudinal 
bearing 40 with the sealing roller 38, the lower edge of which is 
indicated by the broken line 77, are shorter than the path-defining roller 
28. 
The sealing member 75 is, for example, an extruded profile of Santoprene, 
an extrusion of various different grades of Santoprene or an extrusion of 
Santoprene with polypropylene. In all these cases, the Santoprene may be 
foamed or unfoamed. The Santoprene may be replaced by EPDM. The 
polypropylene may be replaced by polybutylterephthalate (PBT). A sealing 
member which is a co-extrusion of EPDM with PBT is also possible. Fillers 
may be included in the sealing material. The sealing member should have 
good chemical resistance and durability. 
In an alternative embodiment, the sealing member 75 is co-extruded with the 
longitudinal bearing 40, especially if formed of polyethylene or 
polypropylene. As can be seen in FIG. 1, a similar sealing member 76 is in 
contact with the second sealing roller 39. 
The end covering 68 of the path-defining roller 28 is in contact with the 
end plate 62. The covering 34 extends beyond the end of the core 32 to 
define a space 44 into which the elastomeric material of the end covering 
68 may be deformed as a result of a sealing force between the end covering 
68 and the sealing roller 38 on the one hand and the end plate 62 on the 
other. 
The path-defining rollers 28, 30 are positioned relative to each other such 
that end face of the first roller 28 lies in the same plane as end face of 
the other roller 30. Each roller is in sealing contact, not only along its 
length with the respective sealing roller 38, 39 but also by its end faces 
with the end plate 62. The end plate 62 is so shaped as to have a lower 
edge 66 which follows a circumferential line around the shaft 54 of the 
first path-defining roller 28 and a circumferential line around the shaft 
of the second path-defining roller 30 to enable the end plate 62 to be in 
face-to-face contact with the end covering 68 of the first path-defining 
roller 28. At its lowest point, the edge 66 is below the level of the nip 
36. The circumferential distance over which the end plate 62 is in contact 
with the end face of the first path-defining roller 28 and the end face of 
the second roller 30 is as low as possible, but is larger than the 
circumferential distance between the nip 36 and the sealing roller 38. 
The end plates 62 are urged against the end faces of the path-defining 
rollers 28, 30 by springs (not shown). A suitable spring force is from 2 
to 500 g/cm of contact between the end plate 62 and the end covering 68 of 
the roller 28 measured at the surface of the roller. The pressure between 
the end face of the path-defining roller 28 and the end plate 62 is at 
least 2.rho.*g*h, which in the case where the height of the treatment 
liquid above the sealing point is 0.4 m means a pressure of at least 9408 
Pa. When the path defining roller has a diameter (.phi.) of 40 mm and the 
width of contact between the end plate and the end face of the roller is 2 
mm over an angle of 90.degree., a force applied to the end plate of 
EQU .pi..phi.4*0.02*9408=5.64 N (.ident.45 g/cm) 
is required to establish this pressure. 
The second sealing roller 39 is similarly constructed and retained in the 
longitudinal bearing 40. The two sealing rollers 38, 39 and the two end 
plates thereby complete a continuous sealing path which, together with the 
roller nip 36 retains the treatment liquid 24 in the vessel 12. 
The end plate 62 includes an aperture 74, the lower edge of which is 
positioned below the level of the top of the path-defining rollers 28, 30, 
enabling the bulk of the treatment liquid 24 to flow out of the vessel at 
each end thereof and to be recirculated as desired. 
A sealing ring 82 surrounds one end of the sealing roller 38 and is urged 
into contact with the end face of the path-defining roller 28 by means of 
a sinus spring 86 acting upon a backing ring 83 in contact with the 
sealing ring 82. The sealing ring 82 has a configuration which, in its 
relaxed condition, is undersized with respect to the sealing roller and 
when mounted on the sealing roller exhibits a flat face 96 to the end 
plate 62, which is fixed to the housing. 
The sealing ring 82 comprises two discrete regions, namely a sealing roller 
contacting region formed of PTFE 95 and sealing surface contacting regions 
formed of EPDM elastomer 94. The sealing ring has a composite structure, 
comprising a spring 92 embedded in the elastomeric material 94. The 
separate spring 92 is optional, so that the composite structure may simply 
consist of a low friction material 95 and an elastomeric material 94. It 
is also possible for the low friction material 95 and the elastomeric 
material 94 to be formed of one and the same material. 
The process for constructing a sealing ring is schematically illustrated in 
FIG. 5. A ring-like member 821 having a non-flat end face 961, is 
provided, which is undersized with respect to the sealing roller 38. The 
ring like member 821 is formed of PTFE 95. The ring-like member 821 
includes cut out portions 88, 89 opening onto an end of the ring-like 
member, and is forced over a mandrel 90 having a size substantiality equal 
to the size of the sealing roller 38. The spring 92 is inserted in cut out 
portion 89 and then both cut out portions 88, 89 are filled with EPDM 94 
so as to provide a sealing ring with a flat end face 96. After filling the 
cut out portions 88, 89 with the EPDM 94 and allowing the latter to 
harden, and while the ring-like member 821 is still positioned over the 
mandrel 90, the end of the ring-like member is ground to provide the flat 
face 96, perpendicular, in use, to the axis 98 of the sealing roller 38. 
Once the EPDM has set, the sealing ring 82 is removed from the mandrel 90 
and then fitted onto one end of the sealing roller 38. 
Alternatively, the sealing roller 38 is itself used as the mandrel 90. 
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Reference Number List 
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vessel 12, 12', 12" 
end plate 62 
housing 14 lower edge 66 
upper part 15 roller end covering 68 
lower part 16 aperture 70 
upper opening 17 surface 71 
lower opening 18 aperture 74 
flanges 19, 21 fixed sealing member 75 
path 20 sealing member 76 
sheet material 22 broken line 77 
arrow A contact regions 80 
liquid 24 groove 81 
surface 25 sealing ring 82 
passage 26 backing ring 83 
path-defining rollers 28, 30 
fixed transverse sealing 85 
core 32 sinus spring 86 
covering 34 cut out portions 88, 89 
nip 36 mandrel 90 
sealing roller 38, 39 
spring 92 
bearing 40 elastomeric material 94 
leakage tray 42 PTFE 95 
space 44 flat end face 96 
distance H axis 98 
roller shaft 54 ring-like member 821 
non-flat end face 961 
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