US2488445A - Apparatus and process useful in making copper oxide rectifiers - Google Patents

Description

Nov. 15, 1949 w. H. SUTTON APPARATUS AND PROCESS USEFUL IN MAKING COPPER OXIDE RECTIFIERS Filed Nov. 13, 1946 INVENTOR Mfl/Gm H. fwfon.

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Patented Nov. 15, 1949 APPARATUS AND PROCESS USEFUL IN MAKING COPPER OXIDE RECTIFIERS William H. Sutton, Pittsburgh, Pa., assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application November 13, 1946, Serial No. 709,502

2 Claims. (Cl. 175-366) My invention relates to methods for producing copper oxide rectifiers, and in particular, relates rectifiers of the prior art.

Still another object of my invention is to provide a means for regulating at will the cooling rate applied to copper oxide rectifiers in a heattreating process used in their manufacture.

Still another object of my invention is to provide a copper oxide rectifier having electrical characteristics which are an improvement over those of the prior art.

Other objects of my invention will become apparent upon reading the following description taken in connection with the drawing in which Figures 1 and 2 are, respectively, a sectional view in front elevation and a sectional view in side elevation of an apparatus adapted to carry out the preferred process involved in my invention.

Substantially all processes for manufacturing copper oxide rectifiers at present in use are modifications of that described in Grondahl Patent 1,840,335, assigned to the Union Switch 8; Signal Company of Swissvale, Pennsylvania, and involve the steps of oxidizing copper at a temperature just below its melting point, annealing it at an intermediate temperature for a moderate period and then cooling it rather rapidly to room temperature. In most factory production processes. the copper units have been cooled from the annealing temperature by dropping them into a water bath. I have found that units subjected to this treatment have a desirably high conductivity to current fiow in the forward, or normally conductive direction, but that they have only a moderate ability to withstand voltages impressed on them in the inverse, or normally non-conductive direction. In their service as rectifiers, such units have, of course, to withstand inverse voltage equal roughly to twice the peak voltage of the alternating current supply to which they are connected, and hence ability to withstand a higher inverse voltage would be a desirable characteristic inasmuch as it would increase the volt- 2 age rating of a rectifier oi a given size. Likewise, high conductivity in the forward direction is desirable inasmuch as it limits the power loss and heating which determine the current rating of a' rectifier of a given size.

I have found that if, after annealing, the cop- Per units be cooled more slowly, for example by allowing them merely to stand in the air of the room instead of plunging them in a water bath, the inverse voltage which they are capable of withstanding is very greatly increased but, unfortunately, the conductivity to current in the forward direction is greatly decreased. Theresuit is that while units subjected to this slower cooling method are superior for high-voltage lowcurrent service, they offer little or no advantage for many types of service in which larger current outputs are desirable.

However, I have discovered that if the rate of cooling is made intermediate between the rapid water quench, and the slow air cooling above described, a range is found in which the ability to withstand inverse voltage is substantially as great as that of the more slowly cooled units, while the conductivity in the forward direction is substantially greater than that of such units, and is in fact only slightly smaller than that of units subjected to water quench.

I have accordingly provided a method andapparatus for conducting the cooling of rectifier units from annealing temperature to room temperature at a rate which can be predetermined at will. While the principles of my invention are applicable in ways readily evident to those skilled in the art to copper oxide rectifiers of any geometric form, I am illustrating it as applied to rectifiers made in the form of rectangular copper plates oxidized on substantially their entire surface. Plate rectifiers of this type are now very widely used in the art, particularly for higher current services, but the modifications of the apparatus I show suitable to operate upon another widely used form of rectifier, namely, the circular disc or washer type, will be too readily apparent to those skilled in the art to require separate illustration.

Referring in detail to Figures 1 and 2, rectangular copper plates I' may be suitably supported in spaced relation on rods 2, and oxidized by heating them to temperatures not far below the melting point of copper in a suitable furnace of any type well known in the art (not shown). Upon removal from the furnace, they may be maintained in a suitable annealing environment for a proper annealing period, and then removed and transferr d. to the cooling apparatus shown in Figures 1 and 2. The rods 2 may be supported on hook-members 3 which may be hung on rods 4 of the apparatus I show. The rods 4 are supported on projecting arms 5 from the links of a conveyor chain running over sprockets 6 and I supported by bearings (not shown) on shafts 8 and 9 which are preferably in the same vertical plane. The shaft 8 may be driven at a suitable speed by any desirable arrangement such as theshaft ll of a variable speed motor [2, the rate of rotation of which may be adjusted in accordance with the systems well known in the art by a variable resistor I-3.

The arms 5 are located at such intervals along the conveyor chains that they are spaced further apart than the length of the rectifier plates I. Since I find that a relatively slow movement of the conveyor chains suffices to produce the desired results with the rectifiers worked upon, it is possible to hang the hooks 3 on the rods 4 during the time that the latter are passing in a downward direction, and it is also possible to remove the hooks 3 from the rods 4 during the time that the brackets 5 are moving in an upward direction in the course of movement of the conveyor chains. Thus, in continuous succession, the downward-moving portion of the chain conveyor is loaded with rectifier plates to .be cooled, and the cooled plates are continuously removed from the upward-moving portion of the conveyor after cooling.

The substantial cooling of the rectifier plates is carried out by allowing them to be slowly immersed in water or other suitable cooling liquid contained in a tank suitably supported, by means not shown, with the surface of the liquid preferably below the lower edge of the sprockets 1.-

tank l5; and this temperature may obviously be determined at will by suitably circulating such liquid through a temperature-determining sysof rectifier plate which has been standardized in commercial manufacture and having the dimensions 12 inches by 4% inches by mils thick, the optimum ratio of inverse voltage rating to load current is attained when the speed of the conveyor chain is from two to three feet per minute.

I claim as my invention:

, 1. The method of manufacturing copper oxide rectifier plates which are about 12" long by 4%" wide by 50 mils thick which comprises the step of cooling them from the annealing temperature to about room temperature by moving them with their longer axis vertical downward into a quenching liquid at a rate of about two to three feet per minute.

2. Apparatus for cooling copper oxide rectifiers having the form of plates about 12" by 4%,"in size .which comprises means for supporting said plates with their planes vertical, and means for moving said plates while supported in said position downward into a quenching bath at a rate of about two to three feet per minute.

WILLIAM H. SUTTON.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,416,811 Frayer et al May 23, 1922 2,070,644 Becker Feb. 16, 1937 2,276,647 Conrad et al. Mar. 17, 1942 2,369,565 Haase Feb. 13, 1945

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