US2153188A - Cathode support for electrolytic units - Google Patents

Description

April" 4, 1939.

K. c. D, HICKMAN SAT1-IODE SUPPORT FOR ELECTROLYTIC UNITS Filed Dec. 17, 1935 INVENTQR:

Patented 4, 19-39.

UNITED STATES PA'rEN'r OFFICE' 2,153,188 carnonn: snrron'r non Emornownc UNITS y f Kenneth C. D. Hickman, Rochester, N. Y., assignor by mesne assignments, to Eastman Kodak Company, JerleyCity, N. J., a corporation o! New Jersey Application December 17, 1935, Serial No. 54,874

The present invention relates to improvements in cathode supports for electrolytic units, and more particularly to means for supporting the cathodes within an electrolytic unit for recovering silver from a used photographic xing bath.

In many of the electrochemical reactions for depositing metal upon cathode plates, and particularly, in the electrolytic deposition of silver from silver` laden fixing baths, priming nuclei are continuallydeposited, and the ,metal deposit spreads from any point where the cathodes touch the wall of the container. In time, this metallic deposit reaches the anode and the cell becomes short circuited.

vision of supports for the cathodes in an elec-Y trolytic unit such that a longer path is providedl for the spontaneous growth of the metal deposit from the cathode.

A further object of the invention is the provision qf cathode supports which induce preferential deposition of the metal away from the contact edge of the cathode.

Still another object of the invention is the reduction to a minimum of the boundary on the cathode where the adverse conditions exist.. r

A still further object of the invention is the provision in an electrolytic unit,provided with an electrolyte agitating means, of a connection between the cell and the cathode,` and including a flexible portion so that the aforementioned spontaneous deposits of metal or silver may be broken up or clearedaway by the circulation oi the electrolyte. I

Other and further objects of the invention will be suggested to those skilled in the art by the description which follows. .y

The above and other objects of the invention are obtained in an electrolytic unit which comprises l a cell for containing the electrolyte, a cathode for immersion in the electrolyte and adapted to re- 'ceive'a plating currenta connection for locat- 50 ing the cathode with respect to the cell, and a member within said connection and having a formation for minimizing the deposit of metal inthe vicinity of 'said connection, and providing a tortuous path for the spontaneous metallic deposit 1 which tends to extend from the cathodeand along The primary object of the present invention is to provide a supporting arrangement for the` Y known manner.

(Cl. zoe-5) the surface oi' the connection and cell to the anode.

Reference is hereby made to the accompanying drawing wherein like reference characters designate similar elements, and wherein:

Fig. 1 is a vertical cross-section of anelec- -trolytic unit in which the cathodes are supported according to the invention.

Fig. 2 is a perspective view of a cathode support and a'member for minimizing the deposit of metall on said support.

Fig. 3 is also a vertical cross-section of an electrolytic unit with two dinerent types of cathode supports.

Fig. 4 is a section taken on the line 4-4 of Fig. 3.

The present invention is applicable to many types of electrolytic units, but for the purposes of illustration is disclosed as applied to a unit which comprises a cell I0 having side walls I I and a bottom wall I2. A rotating shaft I3 extends longitudinally of the cell IIJ and carries a plurality of arms I 4. The side walls II of cell I0 may be provided with grooves I5. The cell III is adapted to contain an electrolyte I6 which may iill the cell I0 to any predetermined level. The electrolyte is selected according to the character of the electrochemical reaction to be performed within the electrolytic unit, and is preferably silver laden photographic xing solution.

A cathode I1 is immersed in the electrolyte and is connected to a source of electrical energy so that a plating current ows from the anode (not.

shown) through the electrolyte I6 and to the cathode I1. This ow of plating current causes deposition of metal upon the cathode I1 in a The preferred form of cathode and cathode supporting arrangement is disclosed in Figs. 1 and 2. The side edges of cathode Il fit into the grooves I5 in the side walls of the cell Ill. Said sideedges of the cathode I1 are cut away as at I8 V so as to be spaced from the side walls II and thel I which are provided along the edges of supporting. blocks 23 on the bottom wall I2 of the cell I0.

Under actual plating conditions there is a natural tendency for the spontaneous deposit of metal to extend from the cathode I1 along the feet members 20 and 2 I and along the walls of the cell I0 to the anode. As before mentioned, such deposit of metal will in time short-circuit the cell.

According to the invention a member is interposed or inserted into the connection between the cathode and the cell and functions to minimize the deposit of metal in the vicinity of said connection. A bell-shaped or skirted member 24 will reduce the spontaneous growth of the metallic deposit to a minimum. Such member 24 has a dome portion 25 which covers the end of the feet 20 or 2| within the grooves I5 or 22 of the side walls II or supporting blocks 2'3. Member 24 also includes a skirt portion 26 which flares out from said dome portion 25, and which surrounds or encircles those portions of the feet members 20 and 2| which extend to the edges of cathode I1. The member 24 may be composed of rigid insulating material, such as glass, Celluloid, hard rubber, Bakelite, etc.

The tortuous or devious path for the plating current leak along the cell and connection to the cathode reduces the spontaneous growth of metal along that path, and in turn reduces the possibility of a short-circuit within the cell. The member 24 may also be composed of a exible insulating material, such as rubber. This composition of the member 24 is particularly useful within cells which require an agitating member because circulation of the electrolyte will then cause flexing of the skirt portion 26 of the member 24 and breaking up of the metallic deposit which is formed along the surface of said member 24. In this way the protective member for lthe cathode connection will be self-cleansing.

It is pointed out that the arrangement for supporting the cathode I1 as disclosed in Figs. 1 and 2 by virtue of the skirt portion 26 of the member 24 reduces or eliminates the undesirable growth of metal from the cathode, either by providing a longer journey forthe deposit from the cathode to the anode, or .by providing a longer path for the electric plating current in the region where the undesirable deposit may start, or by inducing preferential deposition away from the contact edge lof cathode I1. The undesirable deposit is also reduced or eliminated by providing the feet members 20 and 2| so that the area where the adverse conditions exist is reduced to a minimum. Finally, any deposit that may occur is automatically cleared away by reason of the fact that the skirt portion 26 may be ilexible and may be moved by circulation of the electrolyte to break up any deposit that has been formed along the member 24.

Other arrangements for supporting the cathode plate in such an electrolytic unit are disclosed in connection with Figs. 3 and 4. In this case the cathode 21 ts into the grooves I5 of the side walls I| along the entire length of said cathode 21. A strip 28 of insulating material is inserted between the side edges of cathode 21 and said grooves I5. Said strip 28 extends along each side of the edge of cathode 21, and reduces or eliminates the spontaneous deposit of metal from the cathode edge along the walls of cell I0 in the same manner as did the skirted member 24 of the previous form of the invention. 'I'he strip 28 may also be of exible material so that this intervening member will also be self-cleansing upon being ilexed by the circulation of the electrolyte.

Similar but shorter Ilexible strips 29 are inserted between the lower edges of the cathode 21 and the grooves 22 within the supporting blocks 23. As before, these strips 29 are of insulating material and provide a tortuous ordevious path for the spontaneous growth of metal from the cathode, or for the plating current leak along the walls of the cell to the cathode. Also, these strips 29 may be iiexible so as to be movable by circulation of the electrolyte to prevent the deposit of metal therealong or to break up any deposit that may have formed thereon.

Another advantage of the interposed members 24 according to the invention is produced by usg,

of these membersin connection with an electroltig lytic unit in which the electrolyte is circulated. In many electrochemical reactions, and particularly in a deposit of silver from used photographic fixing baths which are vigorously stirred, the rate of deposition is promoted or increased by continually removing the electrolyte, from which the metal has been deposited, away from the cathode.

Conversely, there is very little, if any, metal deposited from a stagnate pool or portions of the electrolyte which are near the cathode. The skirted member 24 protects the electrolyte in the vicinity of feet members 20 and 2| from being circulated by the agitating means consisting of shaft I3 and arms I4. Similarly, the strips 28 and 29 along the edges of cathode 21 provide stagnate bodies of electrolyte along the edges of the cathode, and in this way further reduce the spontaneous deposit of metal along those portions of the cathode. In practical operation these methods of supporting the cathodes have proved indispensible and contribute in a large part to the solution of a diflicult problem-that of removing metallic silver from a used photographic fixing bath.

. Other forms of supports may be designed to include or incorporate the features and advantages of the supports disclosed herein. However, the invention is not to be limited by the illustrated modifications but only by the scope of the ap pended claims.

Having now particularly described my invention what I desire to secure by Letters Patent of the United States and what I claim is:

1. An electrolytic unit for depositing a metal from an electrolyte, comprising a cell adapted to contain the electrolyte to a. predetermined level and having side walls which are provided with grooves, a cathode adapted to be immersed in said electrolyte and having side edges which are cut away below the level vof the electrolyte and which submerged side edges are provided with a recess, a connection attached to said cathode within the recess thereof and for engaging the side walls of` the 4cell to position the cathode therein, and 'a skirt member encircling said connection within said recess and for minimizing the deposition of the metal on said connection.

l 2. An electro-plating unit for depositing metallic silver from a used photographic fixing bath, comprising a cell adapted to contain to a predetermined level said used fixing bath as an electrolyte and having walls which are provided with grooves, a cathode adapted to be immersed in said electrolyte and having edges which engage said grooves above the level of the ilxing bath electrolyte and which are cut away below the level of the electrolyte to be spaced from said side walls, the submerged side edges of said cathing the grooves in said cell to position the cathode therein, and a bell-shaped sheath member having a dome portion between said foot member and the engaged groove and having a vskirt portion extending into the recess of said cathode and encircling said foot member in spaced relation thereto.

3. An electro-plating unit for depositing metallic silver from a used photographic fixing bath, comprising a cell adapted to contain to a predetermined level said used xing bath as an electrolyte and having walls which are provided with grooves, a cathode adapted to be immersed in said electrolyte and having edges which engage said grooves above the level of the nxing bath electrolyte and which are cut away below the level of the electrolyte to be spaced from said side walls, the

submerged side edges of said cathode being iurther provided with a recess, an agitating means for circulating Aelectrolyte acro said cathode, a

' foot member attached to said cathode within the recess thereof and for enteringthe grooves in said cell to position the cathode therein, anda bellshaped sheath member having a dome portion between said root member and the engaged grooves and having a skirt portion extending into the recess of said cathode and providing a devious path for the spontaneous metallic deposit from the edges of said cathode. i

4. An electro-plating unit for depositing metallic silver from a used photographic iixing bath.

comprising a cell adapted to contain to a predetermined level said used fixing bath as an elec-- trolyte and having walls which are provided with grooves, a cathode adapted to be immersed in said electrolyte and having edges which engage said grooves .above the level of the nxing bath .electrolyte and which are cut away below the level of the electrolyte =to be spaced from said 'side walls, the submerged side edges of said cathode being further provided with a recess, an agitating means for circulating electrolyte across said cathode, a root member attachedtosaid cathode within therecess thereof and for entering the grooves in said cell to position the cathode therein, and a bell-shaped sheath member having a dome portion' between said foot member and the engaging t grooves and having a flexible skirt portion sur'- rounding said foot member to provide a stagnant body ofoelectrolyte in the vicinity of said foot member and movable by the circulation oi said electrolyte to dislodge any deposit of metal that may form on said skirt portion.

KENNETH C. D. HICKMAN.

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