US 3840217 A
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United States Patent [191 MacKay 1 SILVER RECOVERY  Inventor: Michael T. MacKay, 2160 I Streamview, Sandy, Utah 84070  Filed: Nov. 2, 1973  Appl. No.: 412,090
 US. Cl. 266/22, 7 5/l09  Int. Cl C22b 11/12  Field of Search 266/12, 22; 75/108, 109, 75/118  References Cited UNITED STATES PATENTS 3,692,291 8/l970 MacKay 266/22 Primary ExaminerGerald A. Dost Attorney, Agent, or Firm-Lynn G. Foster ABSTRACT Equipment and methods for recovering silver from a silver-containing solution. The equipment comprises a plastic container and rotatable spaced T-connectors comprising an influent liquid passage and an effluent liquid passage. A transparent U-shaped tube with an elevated aperture therein spans between the two T- connectors. The influent and effluent liquid passes through fittings in a lid which fittings are externally sealed adjacent respective openings in the lid. The circumference of the lid comprises a female slot ending in a downwardly extending exposed lip or flange. The lid and container are thus joined in releasable press-fit relation during use. The fittings, carried at the mentioned apertures in the lid, are each in two parts, one threaded into the other from opposite sides of the lid. A recovery element made of a metal above silver in the electromotive force series fits within the container. The metal-forming the element is arranged in a woven matrix, such as, for example, galvanized window screen, which is wound upon itself around its longitudinal axis which is offset from but parallel to the axis of the container to form a hollow cylinder having an inside surface and an outside surface and which is transversely pervious in respect to the container. A pedestal of wood with a male extension disposed in the hollow of the coil supports the coil well above the bottom of the container, where sludge collects. The influent passages are in liquid communication with the interior of the container adjacent the outside surface and near the bottom of the element, and the effluent passage is in liquid communication with the hollow interior and near the top of the element. The influent passage terminates within the container in a baffle comprising a T-shaped fitting. The solution precipitates silver in exchange for the metal of the woven matrix.
7 Claims, 3 Drawing Figures PATENTED GET 8 4 II I -FlG.2
SILVER RECOVERY BACKGROUND 1. Field of Invention This invention relates generally to silver recovery and more particularly to a silver recovery unit having an improved structure comprising a plastic container and press-fit lid using rotatable influent T fittings, threaded lid fittings, an eccentric metal fabric coil, a coil pedestal support and a baffled influent opening and effluent openings of substantially different elevations within the container.
2. Prior Art Various silver salts used in photographic paper and film when fixed by various fixatives produce a complex silver salt which is dissolved or suspended in solution. As the fixatives become depleted, replacement is nec: essary to keep the fixing solution at a satisfactory strength if uniform and acceptable results are to be obtained. This replenishment is often accomplished on a continuing basis by the addition of a given volume of concentrated solution of fixatives to the fixing bath, while at the same time an equivalent volume of spent solution is withdrawn.
A technique forrecovering silver from such spent solutions has been developed. The technique requires the passing of solutions containing silver salts through packed steel wool or small cut pieces of galvanized window screen. The steel wool and pieces of screen are anodic to silver so that a chemical replacement action will occur, which causes precipitation and deposition of the silver as the steel wool or pieces of screen dissolve. The disadvantage of packed steel wool has been its lack of resistance to corrosion caused by the fixing solution. Specifically, the steel wool fibers are small in diameter and, therefore, readily dissolved by the solution. The result is that relatively large openings develop in the steel wool and the fixing solution, thereafter, flows through the openings rather than through the remaining packed steel wool fibers since the openings present less resistance to flow. The steel wool must be replaced once the existence of such openings is discovered in order to restore satisfactory efficiency to the silver recovery unit.
Also, silver recovery units of the prior art have been expensive to manufacture, use and maintain. Frequent clogging has occurred and inefficient recovery of silver experienced. Also, flow patterns through prior art silver recovery units have resulted in inefficient recovery of silver because of poor contact with the exchange metal and lack versatility in the placement of such unit has been restrictive.
BRIEF SUMMARY AND OBJECTS OF THE INVENTION The mentioned disadvantages of prior art silver recovery units have been substantially alleviated or overcome by the present invention,-which comprises a plastic container covered by a press-fit plastic lid. Rotatabl'e T-connectors above the lid can be selectively set to direct influent and effluent liquid to and from the container in a plurality of directions. A U-shaped transparent overflow tube joins the two T-connectors. The lid presents spaced apertures with water tight interrelated fittings on each side of the lid at each aperture through which influent and effluent solution passes. So-
lution flow within the container passes a transversely pervious metallic core eccentrically disposed within the container upon a retaining pedestal well above the bottom of the container. The core is constructed from axially oriented, coiled screen with small mesh openings. The influent passage terminates within the container near the bottom at a baffle adjacent the outside of the coil, while the effluent passage commences within the container near the top at the hollow interior of the coil.
The result is that silver recovery units according to the present invention and inexpensive and easy to use, circulation is improved and efficiency is high until the replaceable metallic core has been fully utilized and the operation of the unit is not normally subject to interruptions due to pre-mature clogging. The units may be placed anywhere and solution flow adjusted to suit the physical conditions of placement.
An emergency overflow transparent conduit with a gravity port connects the influent and effluent passageways above the lid to accommodate prompt discharging of influent solution when a surge of solution or unexpected clogging of the container occurs.
It is a primary object of this invention to provide an improved silver recovery apparatus and method.
Another important object of the present invention is to provide an improved silver recovery apparatus and method wherein novel flow mechanisms wherein clogging is alleviated and silver recovery maximized.
It is a further significant object of this invention to provide a silver recovery unit having selectively settable improved solution flow paths.
It is another paramount object of this invention to insure bottom to top solution flow within a silver recovery container with intermediate flow being transverse through a laterally pervious coil of metal.
These and other objects and features of the present invention will become more fully apparent from the following description and appended claims taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a perspective view with parts broken away for clarity of illustration of a presently preferred embodiment of this invention;
FIG- 2 is a longitudinal cross sectional view taken along line 2-2 of FIG. 1; and
FIG. 3'is a fragmentary perspective of the lid of FIG. 1 showing the two T-connectors and the U-shaped overflow tube removed from one T-connector.
DETAILED DESCRIPTIONOF THE ILLUSTRATED EMBODIMENT As shown in FIGS; 1, 2 and 3, a silver recovery unit, generally designated 2, comprises a bucket or container 4, of polyethylene or other suitable chemicallyinert plastic, a lid or closure 6, liquid effluent and influent connector structures 8 and 10, and a metallic core 12, which is located in generally axial relation, within the container 4 and is in liquid communication with the influent connector structure 10 and the effluent connectorstructure 8.
The silver recovery unit 2, as mentioned, comprises container 4, which terminates in an elevated opening at 14 away from which projects a radial lip 16, together with the dish-shaped closure or lid 6. The container 4 and lid 6 are respectively fabricated of material which is inert to the photographic solutions to be treated and are press-fit together so that the lid 6 closes the opening 14 such that the removable lip 16 fits snugly within a matching female groove 18 disposed between two essentially coextensive, though spaced flanges 20 and 22, which comprise part of the lid or closure 6 and extend downwardly. A ribbon of sealant composition (not shown) may be extruded between the flanges 20 and 22 at groove 18 so that a totally impervious fluid seal is established between the container 4 and the lid 6. A suitable sealant composition comprises RTV silicone rubber sealant, manufactured by the General Electric Co., Silicone Products Department, Waterford, New York. Other acceptable sealants are also available.
The closure or lid 6 defines a plate 24 through which two apertures 26 and 28 extend. Each aperture 26 and 28 receives a fitting 30 comprising a hollow housing 32, with a threaded reduced diameter male extension 33, and a hollow interiorly threaded shaft 34. When snugly threaded together each fitting 30 creates a fluid tight relationship with the lid 6. A short plastic tube 36 passes into each housing 32 in press-fit and preferably bonded relation and concentric with the axis (not shown) of the housing 32 and the threaded shaft 34. A further short plastic tube 56 depends from the interior of the more centrally located one of the two fittings 34 in press-fit and preferably bonded relation. Tube 56 is near the top of the container 4 within the hollow of the core 12 and comprises the beginning component of the effluent connector structures 8.
The influent connector structure 10 comprises a relatively long discharge plastic tube 58, which is press-fit in sealed and preferably bonded relation with the lower opening of the most eccentric one of the fittings 34. Thedischarge tube 58 terminates in a T-connector baffle 60, press fit and preferably bonded to the lower end of the tube 58, such that solution is discharged horizontally through opposite discharge opening 61 of the baffle 60. If desired short tubes (not shown) may be press fit into each opening 61 to further distribute influent solution within the container 4 about the coil 12. In each unbonded press-fit union, a firm, liquid-tight seal may be created by extruding a ribbon of suitable nonsetting sealant into the union. When desired, the unit may be readily disassembled by physically separating each unbonded press-fit and each threaded union. By the same token, the lid 6 together with the influent and effluent connector structures 10 and 8 can be unitarily removed from the container 4 by manually releasing the press-fit connection at bead 16. With the lid or closure 6 removed, the metallic core 12, hereinafter more fully described, can be insertedor removed, and the silver sludge deposited by reason of the chemical action between the core 12 and the solution being processed can also be removed.
A T-connector 48 is joined at the top of each short tube 36 in press-fit. unbonded relation. Each T- connector 48 has two openings located vertically one above the other, the lower of the two receiving one short tube 36 as mentioned. A third, horizontal opening is adjustable by rotation of the T-connector about the short tube 36. Thus, the direction of arrival at the influent T-connector 48 may be adjusted to suit the physical circumstances in which the unit 2 is placed in a given installation and the effluent issuing from the effluent T-connector 48 may likewise be directed so as to best suit the circumstances of use of the unit 2. The influent T-connector 48 receives influent solution tube 46 in press-fit relation at the horizontal opening of the T- connector, which may be bonded or unbonded, depending upon preference. Likewise, effluent tube 68 is press-fit into the horizontal opening of effluent T- connector 48 to accommodate discharge.
A flexible U-shaped tube 74 spans between the upper vertically oriented opening of each of the two T- connectors 48 and comprises an overflow path. The tube 74 is transparent to facilitate visual observation of overflow so that the user of the unit 2 may readily ascertain excessive influent solution flow or clogging as the case may be. Gravity pressure is maintained by reason of an elevated aperture 76 at the highest point in the inverted U tube 74.
It is to be appreciated that for gravity flow operation, effluent tube 68 should be slightly lower in elevation than influent tube 46. Use of a coating comprised of stop cock grease between the contiguous surfaces of associated ones of T-connector 48 and short tube 36 and the connection surfaces between connectors 48 and tube 74 will accommodate relative rotation and removal of the mentioned components without creating leakage problems. One of several suitable stop cock greases is identified as Silicone Lubricant manufactured by Dow Coming of Midland, Michigan.
It should be readily apparent that the material or materials from which the components of the influent connector structure 10 and the effluent connector structure 8 are made must inherently comprise plastics which are inert to the silver-containing fixing solution processed through the silver recovery unit 2.
If desired, end 78 of tube 74 can be removed from the upper vertically oriented opening of T fitting 48 thus providing an examination site where the solution being discharged can be inspected or tested.
The metallic core 12 is transversely permeable and comprised of metal which is above silver in the electromotive force series. Although several such metals are known which will perform. satisfactorily, it has been found that iron in the form of woven pervious screen is well suited to this use.
The coiled screen 12 is preferably retained in the illustrated configuration by use of several belt-type or wire like fasteners 84 each of which forms a loop about the coiled screen to retain the generally cylindrical tightly wound configuration. It is convenient to place or replace the coil of metal screen within the container 4 by merely removing the closure 6 from the container 4 and situating the tightly coiled screen in the position illustrated in FIGS. 1 and 2. Consequently, the core 12 defines a longitudinally-extending eccentrically disposed cylinder defining anoutside surface 86 and an inside surface 88.
The bottom 90 of the coil 12 rests on interlocking crossed beams 92 and 94 of a wooden pedestal 95, which beams are slotted so as to fit together in male/- female relation. The coil 12 is held eccentrically stationary with respect to the crossed beams by such means as metal spikes (not shown) extending from the top of the beams 92 and 94 into the coil between the layers thereof.
A male plug 96 is attached to a top pedestal plate 98, and is made from some suitably non-reactive material. The plug is sized and shaped to fit snugly within the lower end of the hollow interior 88 of coil 12 and prevent upward axial flow of solution from space A to interior 88 and also maintain the coil in the illustrated eccentric position. End plate 98 may be made of a flexible material such as rubber sheeting to insure an absence of upward flow from space *A" to interior hollow 88.
The top of the core 12 supports a horizontally oriented thin impervious cover 100 tightly secured to coil 12 by means such as metal spikes (not shown) extending through the cover 100 into the core between the coils thereof. The cover 100 has a central opening 102 which loosely receives the effluent filling 34, thereby forcing the transverse solution flow mentioned earlier. A hole 104 off of center in cover 100 loosely receives tube 58.
Silver-containing sludge once removed from the container 4, is reduced to elemental silver by conventional processes.
The invention may be embodied in other specific forms without departing from the spirit or essential characteristics thereof. The present embodiment is, therefore, to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore to be embraced therein.
What is claimed and desired to be secured by United States Letters Patent is:
l. A fluid tight silver recovery unit accommodating fluid flow therethrough under force of gravity: a container comprising a bucket comprised of plastic material inert to photographic fixing solution, the bucket being closed at one end and along the length thereof and having a large opening at the other end thereof and a lid sized and shaped to close the opening of the container and comprised of plastic material inert to photographic fixing solution, said bucket and lid together presenting opposed mating male-female press-fit sealing adjacent the opening of the bucket for releasably fastening the bucket and the lid together, the lateral dimensions of each being essentially the same, the lid receiving liquid-conducting influent and effluent means comprised of plastic material inert to photographic fixing solution for introducing and removing solution from the container and influent means comprising a T- connector rotatably coupled to adjacent components of said influent means for selectively setting the direction of influent flow of solution, said effluent means comprising a second T-connector rotatably coupled to adjacent components .of said effluent means for selectively setting the direction of effluent flow of solution, the influent means and effluent means each further comprising male and female fittings coupled together in sealed relation against the top and bottom surfaces respectively of the lid, and a hollow coil of transversely pervious exchange metal disposed within the container and said influent means comprising a baffled distal end terminating within the container near the bottom thereof adjacent the'exterior of the coil of metal and said effluent means beginning within the container near the top thereof within the hollow of the coil.
baffled distal end comprises a T-fitting with one vertically oriented passage coupled to an adjacent component of the influent means and two horizontally oriented passages opening communicating solution into the container.
3. The silver recovery unit of claim 1 further comprising:
a flexible transparent inert plastic tube spanning between top vertically oriented passages of said two T-connectors to accommodate solution overflow.
4. The silver recovery unit of claim 3 wherein:
said transparent inert plastic tube is removable from the effluent T-connector to allow for inspection and testing of effluent solution.
5. A fluid tight silver recovery unit accommodating fluid flow therethrough under force of gravity comprising: a container comprising a bucket comprised of plastic material inert to photographic fixing solution and having an opening at one endthereof and a lid sized and shaped to be compatible with the container and comprised of plastic material inert to photographic fixing solution, the bucket and lid being disposed in releasably sealed relation adjacent the bucket opening, the lid comprising two spaced apertures respectively receiving fitting means of material inert to photographic fixing solution respectively in sealed relation with the lid at the associated aperture and each fitting means defining interior passage means for introducing and removing solution from the container utilizing influent means and effluent means respectively comprising said fitting means, a centrally hollow metallic core disposed within the container having a cylindrical configuration and an axis essentially parallel to but eccentric to the axis of the container, the metallic core comprising a metal higher than silverin the electromotive force series and being substantially impervious to fluid flow in the axial direction but defining a plurality of liquid flow paths essentially transverse of the axis of the metallic core, and wherein the influent means terminates at a baffled end thereof immediately adjacent the outside cylindrical surface of the metallic core near the bottom of the bucket and the influent means commences within a central hollow of the core near the top of the bucket. 1
6. The silver recovery unit of claim 5 further comprising:
a pedestal of substantial height interposed between the bottom of the bucket and the core, the core resting thereon, the pedestal being of a material inert to photographic fixing solution.
7. The silver recovery unit of claim 6 wherein:
said pedestal further comprises an upwardly extending male projection, sized and shaped to be compatible with the hollow of the core, extending into said hollow to retain said core in said elevated eccentric disposition within the bucket in parallel relation with the longitudinal axis of the bucket. k