Roller

A roller to be used in apparatus for wet treatment of photographic material comprises a hollow metallic core and two inserts with coupling shafts provided therein. A coat of chemically resistant thermoplastic material is applied around and sealingly surrounds the core to protect it from the corrosive action of media used in the wet treatment process. The outer surface of the thus coated roller is thereupon machined to a high-quality finish.

BACKGROUND OF THE INVENTION 
The present invention relates to rollers, especially to rollers whose 
length greatly exceeds their diameter, which can be used in apparatus for 
wet treatment of strip material, such as photographic roll film or prints. 
The invention also relates to a method of making such rollers. 
In many types of apparatus for wet treatment of photographic films or the 
like, a web or sheet is transported along one or more straight and/or 
U-shaped paths by means of a conveyor system employing a number of rollers 
whose ends are provided with shafts or analogous mounting or coupling 
means for convenient installation in the frame. The rollers are disposed 
singly or in pairs and are normally provided with smooth external surfaces 
to reduce the likelihood of damage to the photosensitive emulsion. The 
surface finish and the material of the rollers depend on the nature of 
fluids which act upon the rollers during treatment of the processed 
material. For example, rollers which are presently used in developing 
tanks for photographic material comprise cores consisting of high-quality 
steel and coats of rubber. Other materials are used for those rollers 
which transport the film in a fixing or rinsing tank. The rollers at the 
drying station normally comprise a stainless core surrounded by a coating 
of phenolic resin. In many instances, the entire roller consists of 
high-quality steel. The manufacturing cost of such a large variety of 
rollers for use in a combined developing, fixing, rinsing and drying 
apparatus is extremely high, especially since the rollers must be produced 
in small numbers. Moreover, an unskilled workman is likely to confuse the 
rollers during assembly so that a roller which can stand the action of 
media in a fixing tank but is installed in the developing tank, or vice 
versa, is likely to be destroyed after a relatively short period of use. 
This can lead to prolonged interruptions in operation and substantial 
losses in output. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a versatile and 
chemically resistant roller which may be mass-produced in large numbers at 
a low cost. 
It is an other object of the invention to provide a roller which may be 
used in all stages of treatment of photographic material, regardless of 
the nature of fluids which come in contact therewith in various portions 
of the developing apparatus. 
It is a further object of the present invention to provide light-weight, 
rugged, reliable and long lasting rollers which can be used 
interchangeably with similar rollers at any one of a plurality of 
processing stations in a photographic developing or like apparatus. 
A concomitant object of the present invention is to provide a roller whose 
surface quality and chemical resistivity satisfy the requirements imposed 
on rollers in various stages of development of photographic material. 
It is a further object of the invention to provide a novel method of 
manufacturing chemically resistant rollers. 
One feature of the invention resides in the provision of a roller which 
comprises a tubular metallic core provided with an external coat of 
chemically resistant thermoplastic material, and two inserts, portions of 
which are received in the end portions of the metallic core and which are 
provided with shafts or analogous coupling or mounting means to facilitate 
the mounting of the roller in a frame or the like. 
The thermoplastic material of the coat is chosen so as to assure permanent 
bonding between the external surface of the metallic core and the coat 
applied thereto. Experience has shown that a roller produced in this 
matter is superior to conventional rollers because the metallic core 
offers the necessary rigidity and resistance to external forces, even 
under most unfavorable conditions, while the coat which contacts the 
material to be treated is chemically resistant, and advantageously also 
wear-resistant, thus protecting the metallic core from the corrosive 
influence of various media being applied to the photographic material 
during treatment. 
The novel features which are considered as characteristic of the invention 
are set forth in particular in the appended claims. The improved roller 
itself, however, both as to its construction and its mode of operation, 
together with additional features and advantages thereof, will be best 
understood upon perusal of the following detailed description of certain 
specific embodiments with reference to the accompanying drawing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
A roller which embodies one form of the invention is shown in FIG. 1. This 
roller comprises a tubular metallic core 1 which is permanently bonded to 
a cylindrical sleeve or coat 2 of thermoplastic material. In the currently 
preferred embodiment, the metallic core 1 is made of aluminum; however, it 
is equally possible to use other materials which are relatively 
inexpensive and are not highly resistant to corrosion, e.g., when 
subjected to the action of chemically active media used in the wet 
treatment of photographic materials. The only important requirement the 
material of the core 1 has to satisfy, in addition to resistance to 
external forces acting upon the roller, is to enter into a permanent bond 
with the material of the coat 2. The currently preferred materials for the 
making of the thermoplastic coat 2 are hard polyvinyl chloride, 
crystalline polyamide, polypropylene, polyethylene or their combinations. 
The thickness of the coat 2 preferably exceeds 2 millimeters. The reasons 
for such rather pronounced thickness will be discussed later in connection 
with the description of steps following the application of the coat 2 to 
the core 1. Even though there is a wide variety of methods of applying 
such a relatively thick coat of thermoplastic material to a cylindrical 
core, the currently preferred method is illustrated in FIG. 2. This method 
is an extrusion process according to which a continuous aluminum tube 1' 
is rotated about its axis and is moved lengthwise by a carriage, not 
shown, in the direction indicated by an arrow so as to advance along an 
extruder nozzle 3 forming part of an extruding apparatus of conventional 
design. However, it is to be understood that this relative movement can 
also be effected in any other known manner, such as moving the extruder 
nozzle 3 longitudinally of the tube 1' while the tube rotates but is held 
against axial movement. 
Plasticized thermoplastic material which is being extruded from the nozzle 
3 forms a strip as a result of rotation of the tube 1' and contacts the 
external surface of the tube to become attached thereto in the form of 
contiguous helical convolutions merging with each other as a result of the 
material of the strip being in a plasticized state, so as to form a 
continuous coat 2'. A support roller 10 is located substantially opposite 
the extruder nozzle 3 to hold the tube against deflection thus keeping 
constant the distance between the orifice of the extruder nozzle and the 
tube to be coated and the thickness of the coat. While this method has 
been described as being used for coating continuous tubes, it is to be 
understood that it can also be used for coating of tubes of finite length. 
Upon completion of the coating operation, the rube 1' with the 
thermoplastic coat 2' applied thereto is subdivided into tubular sections 
each including a metallic core 1 whose external surface is surrounded by a 
portion or sleeve 2 of the coat 2'. The length of the cores 1 equals or 
approximates the desired length of rollers. The thus obtained 
semi-finished product is then clamped at its outer surface, i.e., at the 
outer surface of the sleeve 2, and the end portions 1a of the core 1 are 
counterbored so that their internal diameters exceed the diameters of two 
cylindrical inserts 4. The end faces 1b of the core 1 are bevelled so that 
they flare radially outwardly and may but need not abut against 
complementary surfaces on the flanges 4a of the respective inserts 4. The 
inserts 4 preferably consist of synthetic plastic material which can be 
bonded to the material of the sleeve 2. In the illustrated embodiment, 
each of the inserts 4 is provided with a shaft 5 of stainless steel; 
however, any other supporting and coupling means, such as sockets for 
accommodation of trunnions external to the roller may be used. 
In the presently preferred embodiment, the material of the inserts 4 
corresponds to the material of the sleeve 2. The end portions of the 
sleeve 2 may extend beyond the end faces 1b of the core 1 so that the 
latter need not contact the flanges 4a. These flanges are bonded to the 
sleeve 2 by means of a suitable adhesive, by welding or in any other 
suitable way which insures that the sleeve 2 and flanges 4a form a 
fluidtight and corrosion-resistant envelope around the metallic core 1. 
The inserts 4 are provided with axial bores 4b which receive splined or 
toothed end portions of the respective shafts 5. The shafts 5 are 
permanently attached to the respective inserts 4 by an adhesive, by 
injection of the material of the inserts into a mold into which the 
splined portions of the shaft extend, or by sonic welding. The latter 
procedure consists in subjecting a shaft 5, while being forced into the 
respective insert 4, to vibrations at least in the sonic range, with 
resulting development of heat in the regions immediately bordering and 
contacting the shaft 5, caused by the friction between the surfaces of the 
shaft and the insert with attendant partial melting of the insert. Such 
partial melting facilitates the introduction of the shaft into the insert 
and insures the formation of a permanent bond when the molten material of 
the insert is caused or allowed to set. 
The currently preferred method of manufacturing the roller illustrated in 
FIG. 1 will now be described. As already explained above, the metallic 
tube 1' is first provided with a coat 2' having a sufficient thickness so 
as to allow for subsequent finishing operations, and then cut or otherwise 
subdivided into sections each of which includes a metallic core 1 provided 
with a sleeve 2 and having a length corresponding to the desired length of 
the cylindrical part of the roller. Subsequently thereto, the thus 
obtained semi-finished product is clamped at the inner surface of the core 
1, and the external surface of the sleeve 2 is coarsely machined by 
turning or other material-removing operation so as to provide the sleeve 
with an external surface which is coaxial with the internal surface of the 
core 1. Subsequently thereto, the semi-finished product is clamped at the 
thus coarsely machined external surface, and the end portions 1a of the 
core are counterbored by turning or a similar material-removing operation 
along a length at least matching the length of those portions of the 
inserts 4 which are to be inserted into the core 1. The internal surfaces 
of the end portions 1a are coaxial to the outer surface of the coat 2 and 
to the remaining, nonmachined central portion of the inner surface of the 
core. The inner diameters of the end portions 1a are preferably slightly 
larger than the outer diameters of the main portions of the inserts so as 
to facilitate the introduction of inserts into the respective end portions 
1a. Simultaneously therewith, or subsequently thereto, the metallic core 1 
is provided with the outwardly flaring end faces 1b which are preferably 
recessed in respect to the end portions of the sleeve 2. The next step 
consists in introduction of the inserts 4, which are assumed to be 
provided with the shafts 5, into the respective end portions 1a of the 
core 1 with simultaneous establishment of a permanent bond between the 
flanges 4a of the inserts 4 and the sleeve 2, e.g., by glueing or any 
other procedure insuring a permanent seal and a chemically resistant bond 
between the inserts 4 and the sleeve. One of the alternative methods of 
bonding comprises thermal welding of the flanges 4a to the sleeve 2. 
Subsequently thereto, the thus obtained roller is supported on the shafts 
5 which are coaxial with the core 1 and hence with the outer surface of 
the sleeve 2, and the outer surface is machined to eliminate surface 
roughness in a shaving-or chip-removing operation such as, for instance, 
turning or grinding. Experience has shown that best results are obtained 
if the surface is turned using a diamond cutting tool, the obtainable 
peak-to-valley height amounting to approximately 4 mm. While this surface 
quality is sufficient for most applications of the roller, it can be 
further improved by subsequent chemical smoothing operations, such as 
application of a solvent to the surface to be smoothed, or thermal 
smoothing operations, such as utilizing frictional heat between the 
smoothing tool and the surface to be smoothed, blowing hot air or other 
gas against the surface, or smoothing by radiated heat. Experience gained 
in prolonged tests has shown that the thus obtained rollers satisfy all 
criteria required from them if they are to be utilized in a developing 
apparatus for photographic strip or sheet materials, i.e., that they are 
sufficiently rigid so as not to buckle in actual use while the chemical 
resistivity afforded to them by the coat is sufficient for their 
utilization in all stages of the process. 
The counterboring of the cores 1 can be dispensed with if the tube 1' 
consists of accurately calibrated tubular metallic stock having a constant 
wall thickness. 
FIGS. 3 and 4 show a second embodiment of the improved roller. A metallic 
tube, preferably consisting of aluminum, is cut or otherwise subdivided 
into cores 6 of predetermined length. Subsequently thereto, inserts 7 with 
shafts 8 bonded thereto are introduced into the end portions of the core 
6, and centered therein axially with respect to the core by moving the 
flanges 7a of the inserts 7 into abutment with the respective end faces of 
the core. The outer surfaces 7b of the inserts abut against the inner 
surface of the core 6, thus making the inserts 7 and their shafts 8 
coaxial with the core 6. The material of the inserts 7 is preferably 
identical with that of a thermoplastic sleeve 9 for the core 6. Each shaft 
8 is held in the respective insert 7 by four internal ribs 7c which allows 
for some deformation of the insert if the inner diameter of the core 6 is 
too small to receive the insert without deformation. If inserts of such a 
configuration are used, the machining of the inner surface of the core 6 
can be avoided in most cases. 
The thus obtained semi-finished product, i.e., the core 6 with the inserts 
7 and shafts 8, is then introduced into an injection mold of conventional 
design, which is well known and thus not illustrated. A thermoplastic 
material, preferably the same as the material of the inserts, is then 
injected into the mold so as to provide, in a single operation, a coat or 
envelope 9 around the exposed surfaces of the semi-finished roller and 
fill the voids between the ribs 7c. The injected material is preferably 
hard polyvinyl chloride, but any other suitable material may be used as 
well. According to a presently preferred embodiment, the mold consists of 
two mirror-symmetrical parts which have sockets for the shafts 8 and whose 
inner dimensions exceed the outer dimensions of the exposed surface of the 
roller by the intended thickness of the coat, and the injection openings 
are located so as to face the end faces of the roller and thus the 
inserts. The latter expedient facilitates the penetration of plasticized 
material into the voids between the ribs 7c. Since the thus formed coat 
surrounds all the exposed surfaces, i.e., the external surface of the core 
and the exposed external surfaces of the inserts, these parts are 
automatically sealingly bonded to each other. 
After the core has been coated, the roller is supported by the shafts 8 and 
the external surface of the coat 9 is machined, for instance turned, in 
one or more stages, to obtain the final quality of the surface of the 
roller. 
The manufacturing cost of this roller is even less than that of the roller 
shown in FIG. 1; however, the requirements for the quality of the 
injection molding process are high, since only minute quantity of gaseous 
inclusions in the material being injected into the mold to form the coat 
around the metallic core is permitted. Larger quantity of such inclusions 
or bubbles would result in porousness of the coat 9 and, in addition to 
imparing the quality of the surface of the roller, these inclusions might 
result in loss of protective quality of the coat 9 so that the chemically 
active medium may reach the core and thus corrosion thereof may occur. 
Therefore, it is highly desirable that the quantity of entrapped gas be 
kept to a minimum, advantageously by evacuation of the material to be 
injection molded. 
It has been disclosed above in connection with both embodiments of the 
rollers, that the semi-finished coated rollers are machined for 
improvement of the surface quality of the rollers. Thus, it is evident, 
that the coat of the rollers has to have sufficient thickness to allow for 
removal of a portion thereof during the machining operations. As already 
mentioned above, it is desirable that the coat be at least 2 millimeters 
thick. The additional advantages gained by providing such relatively thick 
coating are that even if the core is not completely rotationally 
symmetrical, the material-removing operations will not remove all of the 
chemically resistant coating in some regions of the roller, so that the 
core may be allowed to deviate from the ideal cylindrical shape to a 
certain degree without substantially impairing the lifetime or performance 
of the roller. In addition thereto, the substantial thickness increases 
the lifespan of the roller by providing a larger quantity of material 
which can be worn off before the metallic core is expoed. 
The thus manufactured roller, which has a surface of high quality, is 
superior to heretofore used rubber of rubber-coated rollers. For example, 
the improved roller is not likely to accumulate remnants of gelatin. This 
is particularly advantageous since the removal of gelatin from 
rubber-coated rollers presents many problems. Moreover, the improved 
rollers are less susceptible than any of the heretofore known rollers to 
wear resulting from contact and friction between the rollers and conveyed 
photographic material, particularly to wear resulting from the action of 
leading edges of webs of photographic material upon the surfaces of the 
rollers. 
It will be understood that each of the rollers described above, or two or 
more together, may also find a useful application in other types of 
apparatus differing from the type described above. 
While the invention has been illustrated and described as embodied in 
apparatus for wet treatment of photographic materials, it is not intended 
to be limited to the details shown, since various modifications and 
structural changes may be made without departing in any way from the 
spirit of the present invention. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpont of prior art, fairly constitute essential 
characteristics of the generic or specific aspects of our contribution to 
the art and, therefore, such adaptations should and are intended to be 
comprehended within the meaning and range of equivalence of the claims.