Патент USA US2279580код для вставки
-Àprìl 14,-1942. R . v. MiNER ` 2y,2 79,580 APPARATUS FOR TREATING ARTICLES COATED WITH A CONCENTRATED . AQUEOUS- SOLUTIONv OF GOLD CYANIDE ' Filed Dec. 9, 1939 V . ` ¿r5.7 faw. ¿from? I - Patented Àpr. 14, 1942 _ 2,279,58cî ‘ UNi'î'ED STATES PATENT OFFICE 2,279,580 APPARATUS FOR. TREATING ARTICLES COATED WÍTH CONCENTRATED AQUEO’US SOLUTIONS OF GOLD CYANIDE Robert V. Miner, Chicago, Ill., assigner to Western Electric Company, Incorporated, New York, N. Y., a corporation of New York Application Decemberß, 1939, Serial No. 368,398 l Claim. (Cl. 26S-4Z) for electrodepositing a coatingfoi gold on an This invention relates to electroplating, and article with a minimum loss of gold. The ap more particularly to the electroplating of articles paratus comprises a plating tank and two tanks with precious metals such as gold. containing wash water adjacent thereto in which An object of this invention is the provision of improved methods and apparatus for produc Cil the plated parts are immersed successively. Wash water is withdrawn continuously from the ing plated coatings of gold and other precious iirst tank, circulated through a series of cyl metals on articles with a minimum loss of pre inders containing zinc turnings which precipi cious metal. tate and extract the gold, and then discharged it is customary to electroplate articles in an into the second wash tank. An overflow is pro electrolytic solution of the desired coating metal vided between the first and second tanks so that and then wash the articles in water to remove the ñrst tank is constantly supplied with water the plating solution therefrom. This practice results in the steady withdrawal or drag-out of solution, with the contained metal, from the plating bath on the surfaces of the articles. This prospective loss of metal is not serious in the usual plating process where relatively inex pensive metal solutions are employed, but when from the second tank. In this manner the wash water is constantly recirculated and the gold content in the second wash tank, which deter mine the drag-out loss, is> maintained at a very low value. Following is a more detailed description of the invention, taken in conjunction with the append -gold or other precious metals are used in the - ed drawing, in which the single figure is a sche-y plating bath, the value of the withdrawn solu- » tion mounts rapidly. Consequently, means have been employed to partially recover metal from the drag-out solution in precious metal plating operations. matic drawing of an apparatus incorporating certain features of the invention. In this apparatus and method a conventional plating tank lll provided with the usual elec Under one former practice the plated articles 25 trodes and power supply (not shown) is em were Washed successively in a series of still water tanks and the metal Was extracted from the wash water at intervals. The metal content of the wash tanks was built up progressively, with the smallest metal content in the last tank, which determined the minimum metal loss. The >rate of metal loss was progressive, as the metal con tent of the last wash tank increased steadily with ployed. The tank contains plating solution, such as a sodium gold cyanide solution and the arti cles are plated while suspended in the solution in accordance with the usual practice. Immediately adjacent to the plating tank are two open top wash tanks Il and I2 in which they articles are washed successively after they are removed from the plating solution. The Wash changed constantly and also because of practical tanks can be made of various easily formed ma terials, such as wood, concrete or metal and are conveniently made in one body with an inter limitations in the number of tanks that could be used in the series and the necessity for inter rupting the entire process for any changes in first or initial wash tank H and the second or iinal wash tank I2. use. It was diiîcult to hold this value to desir ably low levels because the metal content the tank arrangements. Due to the handling and processing involved, it was considered nec essary to have a fairly high gold content in the mediate partition l3 between them to form the At the beginning of the process both wash tanks are ñlled with distilled water. As more and more articles are removed from the plating tank and immersed in the wash tanks the total preliminary wash tanks, with a relatively high quantity of gold cyanide flushed from the sur metal content in the iinal tanks, to justify the metal recovery operations. Another objection 45 faces of the articles into the Wash water in the initial wash tank tends to build up rapidly. At to the former practice was the necessity for a the Sametime the gold cyanide content of the final cleaning operation on some parts. For ex ñnal or second wash tank also tends to increase, ample, on certain parts plated in gold cyanide but in smaller unit quantities, due to drag-out it is necessary to remove all traces of the plating from the ñrst wash tank. Ordinarily, any- drag solution, Because the final wash tank in the out from the second wash tank would be lost series contained some, and an unknown quan and in order to minimize this loss, means vare tity of plating solution, these parts received a provided for removing the gold from the wash final washing in running water. water as rapidly as it is deposited therein. ' In accordance with one embodiment of this Wash water is withdrawn continuously from invention, a process and apparatus are provided 55 2 2,279,580 the ñrst Wash tank I I through a pipe I4 having a. manual control valve I5 therein and connected to an opening near the bottom of the tank. 'I‘he wash water is withdrawn by means of a suit ably driven pump I6 connected to the pipe. the oldest zinc, successively with zinc of lesser service age, finally with the freshest zinc just before the water is discharged into the iinal wash tank. With the above described apparatus the loss of gold is very low. When plating with a sodium gold cyanide solution of the usual concentration The pump forces the Wash water through a pipe I1 into a lower header I8. Extending from the lower header are ñve spaced branch pipes the gold content of the ñrst wash tank may run I9, 20, ZI, 22 and 23, each having a manual con around .013 ounce per gallon of water. By cir trol valve 24, 25, 26, 21 and 28 therein. The 10 culating this wash water through the extraction upper end of each branch pipe is connected into tubes or cylinders continuously the gold content the bottom end of a hollow cylinder 29, 30, 3|, of the second or final wash tank, which deter 32 and 33. Each of the ñVe cylinders contains mines the drag-out loss, can be maintained con a quantity or batch of zinc turnings 34. Connected into the top of each of the four 15 sistently at a value as low as .O03 ounce per gallon of water. The resultant gold loss is in cylinders on the left in the drawing (cylinders significant compared with the rate of loss under 29, 3U, 3I and 32) is a branched pipe with one former methods. branch thereof 35, 36, 31 and 38, under control The above described apparatus and methods of a manual valve 39, 40, 4l and 42, joined to the pipe running into the next adjacent cylinder 20 can be adapted for plating articles with other solutions and metals by merely using a suitable to the right. The other branch 43, 44, 45 and extracting agent for the selected metal or solu 46 of each of these branched pipes contains a tion in the tubes or cylinders. It will be apparent manual valve 41, 48, 49 and 50 and is connected that other modifications and adaptations of the into a common upper header 5I. The right methods and apparatus are feasible and it is to hand cylinder 33 is also connected into the header through a pipe 52 with a Valve 53 there 25 be understood that the invention is limited only by the scc-pe of the appended claim, in, and with the left hand cylinder 29 through What is claimed is: another pipe 54 with a manual valve 55 therein. Apparatus for treating articles coated with a A pipe 56 connects the upper header with an inlet into the second or final wash tank I2. In 30 concentrated aqueous solution of gold cyanide such as is employed in a gold plating bath to the top portion of the partition I3 between the remove said solution from the article surfaces two wash tanks is an opening 51 through which and recover the gold from said solution, an initial wash water flows from the second Wash tank I2 wash tank containing a dilute4 aqueous solution to the first wash tank Il. . of gold cyanide for receiving the articles coated With the above described system of piping, with the concentrated solution and ñushing the valves and pumps, it is possible to withdraw the concentrated solution from the articles, said di wash -water from the ñrst tank, circulate it lute solution having a maximum gold content of through the complete series of cylinders begin .013 ounce per gallon, a second wash tank con ning with any one of the cylinders, and then taining ñnal wash water for flushing from the discharge the water into the second or final wash articles the dilute solution withdrawn on the tank. articles from the initial wash tank, said final As the wash water is brought into contact with wash water having a maximum gold content of the zinc turnings in the cylinders, the gold is .003 ounce per gallon, means for withdrawing precipitated from the cyanide solution and de posited in the cylinders, from which it is re 45 dilute solution from the initial wash tank at a uniform rate, means for supplying final wash moved periodically. The cylinders or tubes are water from the second tank to the initial tank easily dismantled for removal of the accumulated at the ysame rate at which dilute solution is gold by removing a threaded cap on the tube Withdrawn from the initial tank to maintain a into which the connecting pipes are joined. constant quantity of solution in the initial tank, For maximum gold extraction it is desirable a series of containers each having zinc therein, to contact the solution with fresher zinc as the the containers being connected in series and the solution is weakened by partial gold extraction. zinc in said containers being of successively grad To accomplish this, the Zinc is replaced in one uated age, a system of pipes interconnecting the cylinder at a time, in sequence and at uniform time intervals. For example, one cylinder is re 55 two wash tanks and the series of containers, and a pump for circulating. all of the dilute solution plenished one week, the next cylinder to the right, or the next in the series, is replenished one week later, and so on. Under this practice, the zinc in successive cylinders in the series is of graduated service age; The circulation of wash withdrawn from the initial wash tank through the series of containers beginning with any se lected container and ñnally delivering all of the treated solution to the second wash tank to main tain a uniform supply of ñnal wash water in the Water through the cylinders is controlled, by 60 second tank. means of the valves in the interconnecting pipes, to bring the wash water in contact lirst with ~ ROBERT V. MINER.