Note: Descriptions are shown in the official language in which they were submitted.
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SILVER RECOVERY UNIT
1 BACKGROUND OF THE INVENTION
Field of the Invention
This invention relates to the art of silver recovery
and, more particularly, to a gravity flow apparatus for use in
the recovery of silver from spent photographic fixer solution.
Description of Prior ~rt
A number of devices employing containers for recovering
silver from spent fixing solutions in photographic paper and
film processes are known in the industry. These devices
generally entail passing the solution containing silver salts
through a metal which is above silver in the electromotive
force series. The resultant chemical replacement action
causes silver to be deposited within the container as the
metal is dissolved. When the metal is exhausted, the contents
of the container are processed at a refinery to recover the
silver therein.
U.S. Patent No. 3,369,801, which issued to Harlan G.
Hartman on February 20, 1968, discloses a vessel in which the
solution flows downward through a core tube to the bottom of
the vessel and thence upward through steel wool to an outlet
in the top of the vessel. The chemical reaction referred to
above results in the deposition of silver within the vessel as
the steel wool dissolves~
Window screen is used as the filler material in U.S.
Patent No. 3,630,505, which issued to Byron R. MacKay on
December 28, 1971. The screen wire is therein said to be an
improvement because steel wool fibers are quite small in
diameter and are easily dissolved. As a consequence, large
openings providing less resistive paths are created, permitting
the solution to bypass the filler material and to exit the
vessel with the silver remaining in solution. In Patent No.
3,630,505 the solution fluid is directed through a flow path
from the inside surface of the container, through the screen~
and upward from the bottom of the core tubing.
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1 U.S. Patent No. 3,655,175, which issued to Victor
Zeleny, et al on April 11, 1972, discloses a cannister in
which the solution flows from the bottom of the core tube
upwaxd through metal shavings and a bed of neutralizing
material of alkaline earth metal carbonates. Patent No.
3,655,175 also discloses hori~ontal spacers or baffles separating
the layers of shavings to prevent short circuitry of the
solution as it flows upward through the filler material.
U.S. Patent No. 3,840,217, which issued ~o Michael
10 T. ~acKay on October 8, 1974, discloses a plastic container
with influent and effluent liquid passages in the form of T-
connectors in its lid. The lower end of the influent tube is
a T-shaped baffle for dispersing the influent solution. A V-
shaped tube is connected between the influent and effluent
connectors to accomodate solution overflow. Furthermore, the
U-shaped tube is removable from the effluent connector to
permit testing of the effluent solution to determine whether
silver is being efficiently removed from the solution.
SUMMARY OF THE lNvhN~ ON
The efficiency and the ease of operation of the
prior art devices, including the patented containers discussed
above, vary according to the structural and operational
characteristics of each. The performance of the prior art
~5 has been substantially improved upon by the novel structure
embodied in the present invention. An elongated core is
provided with an aperture in its side for receiving fluid
which has passed through the filler material. A filler of
wound wire provides a large amount of surface area for
contact with and chemical reaction with the fixer solution.
Furthermore, a system of baffles increases the length of the
flow path of solution within the vessel, increasing the
efficiency of the reactive process occurring therein. Inlet
and outlet connections are provided on the side of the
container to permit easier connection and disconnection by
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1 the user. A bypass system is provided to direct fluid from
the influent passage to the effluent passage in the event the
core or the filler becomes clogged. In addition, an opening
is provided in the lid of the container to pexmit inspection
of the filler so that the user can visually determine when the
filler has been exhausted.
It is, therefore, an object of the present invention
to provide an improved silver recovery cannister for recovering
silver from fluid solutions containing silver ions.
Another object of the present invention is the
provision of a silver recovery vessel with improved efficiency
over prior art devices.
Yet another object of the present invention is the
provision of a filler with large surface area and m;n;~l
susceptibility to corrosion and dissolution, so as to reduce
the occurrence of resistance-free, non-reactive flow paths
within the filler.
A further object of the present invention is the
provision of an extended flow path within a silver recovery
container without an increase in the size of the container.
A still further object or the present invention is
the provision of a silver recovery cannister that can be
easily connected or disconnected by the user.
A still further object of the present invention is
the provision of a bypass of the core and filler in the event
that solution is unable to pass through either.
Another object of the present invention is the
provision of a silver recovery cannister which easily permits
the user to visually inspect the filler material.
Other and further objects, features, and advantages
will be apparent from the following description of presently
preferred embodiments of the invention, given for the purpose
of disclosure, when taken in conjunction with the accompanying
drawin~s.
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1 BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be more readily understood from
a reading of the following specification and by references to
the accompanying drawings, forming a part thereof, wherein
examples of embodiments of the invention are shown, and
wherein:
Figure 1 is an elevation view, with a p~rtion in
cross-section, of an embodiment of the present invention.
Figure 2 is an exploded perspective view of a
portion of the embodiment shown in Figure 1.
Figure 3A is a cross-sectional view taken along
lines 3-3 of Figure 1.
Figure 3B is a partial cross-sectional view of an
alternative embodiment of the invention, as taken along lines
3-3 of Figure 1.
DESCRIPTION OF PRE~ERRED EMBODIMENTS
By way o~ illustration and not limitation, this
detailed description presents preferred embodiments of the
invention. It will be readily apparent to one skilled in this
art that the device can be incorporated in manners similar to
the way in which it is here illustr2ted without departing from
the scope of my invention.
Referring to the drawing, the reference numeral 1
2S designates the wall of the container which forms the housing
for this apparatus. In the embodiment illustrated in Figure
1, the container is a bucket with a flat bottom 2~ and a
removable lid 25 which fastens to the container wall 1 in a
press-f~t assembly. The container components are preferably
constructed oE plastic material so as to be lightweight and
inert to the photographic fixing soiution. Also illustrated
in Figure 1 is viewing cap 26, which provides the user with
a means for viewing the contents of the container, without
disrupting its operation, in order to determine whether the
unit is operating properly and whether the filler material has
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1 been depleted. Viewing cap 26 may be made of clear plastic
and friction-fitted to shoulder 27 in lid 25, as shown.
Alternatively, cap 26 may be threaded to permit engagement
with threads (not shown) on shoulder 27. Other forms of
viewing caps may also be used. Viewing cap 26 may even be
made of opaque material, in which event cap 26 must be physically
removed from lid 25 to permit inspection of the contents.
Although not shown in the drawing, the fluid-tightness of the
lid-wall assembly may be enhanced by providing a sealing ring
in the perimeter area ~f the lid 25 in a manner well known in
the art.
Fluid influent means 4 in the preferred embodiment
is shown provided in the form OI a passageway through the
container wall 1 at an influent opening 5 substantially near
the upper portion of wall 1. Influent means 4 may be constructed
in a number of manners well known in the art so as to provide
an inert passageway from the user's fixing solution to the
upper level of the container interior. In the preferred
embodiment, 3/4 inch Schedule 40 PVC tubing is threaded on one
end to receive a sim-ilarly threaded and mating fitting through
influent opening 5 from an influent line (not shown) through
which solution flows from the user's processing equipment. O-
rings 28, on either side of influent opening 5~ enhance the
fluid-tightness of the influent means assembly 4.
Effluent opening 15 is a similar openin~ in container
wall 1, but is located at a height below that of influent
opening 5 so that gravity forces the flow of solution through
the container from influent opening 5 to effluent opening
15. Fluid effluent means 23 is preferably constructed in
like manner to influent means 4 and provides a passageway
through the container wall 1 for solution that has been
processed by the silver recovery container of this invention.
The location of influent means 4 and effluent means 29 on
the side wall of the container, as shown in the illustrated
embodiment, permits -the connection and disconnection of the
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1 cannister from the user's equipment without the necessity of
removal of lid 25. Placement of the inlet and outlet line in
the side of the container is also advantageous over prior art
devices where those lines are connected through the top of
the container. With the prior art construction it is necessary
to have a good seal on the lid as well as on the junctions of
the inlet and outlet lines to the conntainer. With the
preferred construction disclosed herein, the seal on the lid
is less critical. Furthermore, the illustrated structure
permits the user to remove the cannister when the ~iller has
been exhausted and to connect a new cannister to his equipment
merely by rem~ving the external connectors (not shown) that
engage influent and effluent means ~ and 29. No complicated
equipment is required, no unusual mechanical skill is required,
and the user need not comprehend the operation of the cannister
to make the physical connection or removal from his system.
Once a used cannister is removed and replaced by a fresh one,
the user need not do anything with the cannister; the lid
remains in place until refinery personnel remove it to extract
the silver desposited therein.
Preferably in the center of the vessel, and preferably
formed generally in a hollow, elongated, cylindrical shape is
core 12. Core 12 is closed at its lower end, which closure
may be accomplished by molding or by insertion of core plugs
13 which can be press-fitted, adhesively bonded, or otherwise
inserted into core 12 to prevent solution from entering tube
12 through its otherwise-open lower end. As mentioned, in the
illustrated embodiment, the axis of core 12 coincides with the
vertical axis of the container, although the device of the
3~ present invention is not limited to such construction.
A novel feature of core 12 is the aperture 17 in the
side th~reof. The aperture 17 provides an opening for solution
to pass through the wall of the core into the longitudinal
passageway in the core interior and, thence, on to effluent
means 19. Of course, core 12 is~ like all of the components
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1 shown in Figure 2, constructed of material inert to the
solution. Figure 2 illustrates the preferred core construction,
with the aperture 17 extending substantially the length of
core 12 so that the illustrated elongated aperture 17 forms a
slot in core 12 from core plug 13 to the core threaded connector
30 at the core's upper end. The benefits of this novel and
non-obvious construction will be apparent from the discussion
below.
The core 12 is connected to effluent means 29 in the
preferred embodiment via connector 16, core connector 3, and
effluent hose 7. Splash guard 8 is also connected to this
assembly, as shown, and, because of its location below the
influent means 4, serves to disperse fluid entering the
container so that such fluid is distributed generally about
the interior of the vessel. Additionally, splash guard 8
serves to prevent solution from bypassing the filler 11 and
entering the top of core 12, and splash guard 8 provides
support of the core assembly in the event that the unit is
turned on its side. Although shown in rectangular fashion in
the illustrated embodiment, the precise shape of splash guard
8 is not limited to that configuration. Preferably, guard 8
is constructed of clear plastic to permit inspection of a
greater portion of the riller 11, such as when an inspection
is made by the user through viewing cap 26.
In the illustrated assembly, core connector 3 is a
T-shaped tube transforming the flow of fluid from its upwardly
vertical path in the interior of core 12 to a substantially
horizontal path outward to effluent means 29 and ~ffluent
opening 5. Effluent hose 7 may be constructed as a separate
coupler between core connector 3 and effluent means 29, and
may be made of flexible vinyl to provide easier connections
therewith and to prevent its breakage if the core assembly is
rotated. Such connections should, of course, be fluid tight.
If foreign matter gets into the vessel and clogs
core 12 or any of the other elements hereinafter described,
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1 the level of fluid in the vessel will continue to rise since
its path to the effluent openiny 15, as described below, will
be blocked. In such an event, it is desirable to provide an
outlet for the solution so that the container does not continue
to fill until it bursts. Core connector 3 is provided with
overflow opening 2 at a height above effluent opening 15 to
serve such a purpose. In the event that the aforementioned
blockage occurs, the 1uid level in the container rises only
until it reaches the overflow opening 2, Thereafter, the
solu-tion flows downward through core connector 3 and through
effluent means 29 out of the vessel. The user of the cannister,
when making a periodic visual inspection of the interior
through viewing cap 26, will observe the level of the solution,
discern that a blockage has occurred, and replace the defective
cannister with a new one.
In one of the simpler embodiments of the present
invention, filler material 11 is disposed about core 12
between the lower surface of splash guard 8 and the upper
surface of container bottom 24. As taught in the prior art
discussed above, such filler 11 is formed of a metal above
silver in the electromotive force series. Devices of the
prior art commonly utilize steel wool or woven screen wire
for filler, and those materials are likewise appropriate
fillers for use in the device of the present invention.
There are, however, certain disadvantages inherent in some of
these known fillers. For instance, steel wool lacks resistance
to corrosion caused by the fixing solution and is subject to
uneven dissolution, so that resistance-free openings are
formed in the filler 11. These openings permit fluid to pass
through without the desired ion exchange occurring. Some
existing filler materials have also been known to expand and
burst the container, creating a messy loss to the user. Steel
wool has also been known to soak up some undesirable elements,
such as sulphur, making the subsequent processing more difficult.
~n additional material that has been found suitable
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1 for use in the present invention, and which is believed to be
a novel and improved fiIler, is wound steel wire. The wire
may be wound in the fashion of a spool about the core 12 to
provide a filler 11 of desired capacity. When such a filler
is used, however/ the wire should not be wrapped so tightly as
to prevent the filler from being transversely permeable. It
will be appreciated by those skilled in th~ art that the
diameter of the filler spool 11 may be varied, within limits
posed by the size of the particular container utilized, so as
to provide recovery units of varying capacity. Large users
can be provided with a large cannister substantially filled
from its core 12 to the container wall 1 with filler 11.
Smaller users can perhaps make more efficient use of lesser
containers or of uniform containers with lesser amounts of
filler within. Steel wire having a diameter of .003 inch has
been found suitable for this filler, although the invention is
not limited to wound wire of that dimension, or to wound wire
at all~ as even the previously kno~n filler materials can be
accomodated in a vessel of this novel structure and operation.
It will be appreciated, however, that low carbon steel wire
may be preferred because of its cheap cost. The illustrated
embodiment includes filler fastener 10 for providing support
along the periphery of filler 11. Fastener 10 may take the
form of a metal band, staples, a rubberband, or any similar
device suitable for supporting the fi~ler within its intended
confines in the vessel interior.
The invention discussed above is yet further improved
upon by the addition of a baffle structure of a fashion
illustrated in the accompanying drawings. For example, in the
preferred embodiment, support baffle 9 is generally disposed
about the periphery of core 12 and has an axis common to that
of core 12. PVC has been found suitable for constructing said
support baffle 9. Filler 11 is placed in the area between the
outer wall of the core 12 and the inner wall of support baffle
9. Additional filler is formed about the outer surface of
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3~Z~56391
1 support baffle 9, thereby providing two layers of filler
separated by support baffle 9. Support baffle 9 is provided
with an aperture 18 in the wall thereof to permit the flow of
solution from the outer layer of filler to the inner layer.
The drawing illustrates a preferred embodiment of support
baffle 9 in which the aperture 18 in the wall thereof extends
longitudinally the length of baffle 9 to form a slot similar
to that of the core aperture 17. A still more preferred
embodiment, illustrated in Figure 2, disposes apertures 17 and
18 in opposite directions. This construction, also novel in
the art, extends the length of the flow path of solution
through a filler of any given diameter, exposing a greater
portion of the filler to any given volume of solution, thereby
increasing the efficiency with which the filler 11 displaces
silver in the solution.
In the illustrated embodiment, the upper edge of
support baffle 9 is conventionally connected in a fluid-
tight manner to the lower surface of splash guard 8, while
its lower edge is similarly connected in fluid tight fashion
to the upper surface of filler support 14. Filler support
14 prevenis solution from bypassing the filler 11 and flowing
directly to core 12. It also serves to center the core
assembly within the cannister in the event the cannister is
turned on its side. With this configuration, solution
entering the vessel through influent means 4 is dispersed
generally to the peripheral surface of the outer layer of
filler 11 (although filler 11 can extend to the inner surface
of wall 1 of the container). Fluid then flows through the
outer filler layer towards the outer surface of support
baffle 9, thence through support baffle aperture 18. The
solution traverses the inner layer of filler 11 toward the
outer surface of core 12 and around to and through core
aperture 17. Having passed through the multi-layered filler
and the silver salts therein having reacted with the filler
metal, the effluent solution travels the previously described
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1 path through the effluent opening of the vessel.
A still further and patentably distinct embodiment
entails the inclusion of additional baffles interspersed
within the several layers of filler 11. Figure 3B illustrates
the use of baffles 22 and 23 within -the filler material
situated between core 12 and support baffle 9. Baffles 22 and
23 need not be constructed of weight-supportive material like
that used in support baffle 9. Instead, it has been determined,
for instance, that heavy guage plastic sheeting, preferably
disposed concentrically with core 12 and support baffle 9,
functions adequately.
In -the preferred embodiment, with the additional
baffles, whether situated between core 12 and support baffle
9, as shown in Figure 3B, and/or situated between support
baffle 9 and the periphery of filler 11, as shown in Figure
3A, the aperture in each pariicular baffle is placed in the
opposite direction of the apertures of the baffle, or the
support baffle, or the core on either side of the particular
baffle under ~m;nation. As an example, the aperture 31 in
20 baffle 23 is generally revolved 180 degrees from the apertures
17 and 32 in core 12 and baffle 22 respectively. Similarly,
the aperture 33 in baffle 21, located between support baffle
9 and the periphery of the filler 11, is generally revolved
180~ degrees from apertures 18 and 34 in support baffle 9
and baffle 20 respectively. This construction is preferably
continued throughout the layers of filler and baffles 19,
20, 21, and etc., thereby multiplying the benefits of extended
flow paths as discussed above. With this alternating positioning
of baf1e apertures, aperture 18 in support baffle 9 may or
may not be in the illustrated opposite direction from aperture
17 of core 12, depending om whether there is an odd or even
number of baffles situated between core 12 and support
baffle 9. Various other changes may be made, such as the
inclusion of additional support baffles, or the exclusion of
the support baffle 9 altogether, depending on the desired
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1 size and capacity of the particular vessel, without departing
from the teachings or the spirit of this invention.
With the extended flow path of this structure, it
will be seen that the effective surface area of metal filler
11 is increased, and the exposure of solution to filler is
greatly enhanced, for any given size vessel or any given
weight of filler. Furthermore, while the preferred embodiment
incorporates wound steel wire for each layer of filler 11,
conventional filler, such as steel wool, can be used. If
steel wool is, in fact, used in this invention, its previous
disadvantages are somewhat eliminated by this new manner of
construction. For example, one of steel wool's major drawbacks
is its susceptibility to partial dissolution so that resistance-
free flow paths are formed in which the solution fails to
react with the filler. With the sandwich construction of
filler and baffles of the present invention, dissolution of
filler in one layer does not permit the solution to bypass
the remaining filler. This obtains for the user a more
efficient and economical use of his recovery cannister.
The present invention, therefore, is well adapted
to carry out the objects and attain the ends and advantagesmentioned as well as those inherent therein. While presently
preferred embodiments of the invention have been given for
the purpose of disclosure, numerous changes in the details
of construction and arrangement of parts can be made which
will readily suggest themselves to those skilled in the art
and which are encompassed within the spirit of the invention
and the scope of the appended claims.
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