US1908039A - Electrolytic rectifier - Google Patents

Description

M y 1933. R. D. MERSHON ELECTROLYTIC RECTIFIER Filed Nov. 1930 i i 4 7 I 1005 (190 Q t Patented May 9, 1933 PATENT OFFICE RALPH D. MERSHON, OF NEW YORK, N. Y.

ELECTROLYTIC nnc'rrrma Application fled November 18, 1980. Serial. No. 496,441.

' This invention relates to electrolytic rectifiers, for converting alternating voltage and current into direct. As is well known, such devices depend for their operation upon the film which may be formed upon the surface of certain metals and which possesses the peculiar property of offering low resistance to the flow of current from the electrolyte to the metal but relatively high resistance to current tending to flow from the metal to the electrolyte. If, when, an electrode having such a film and an electrode of non-filming metal or other conducting material are immersed in a suitable electrolyte and the two are connected to a source of alternating current only the current impulses which are positive with respect to the filmed electrode will be suppressed and those which are positive with respect to the non-filming electrode will pass through the f Hence the current from the filmed rode will be unidirectional, though more or less pulsating in character. If two filmed Q electrodes are used both current impulses of each cycle may be rectified.

By reason of their simplicity and relatively low cost'such devices ofi'er attractive bilities, but these possibilities have been d difiicult to realize in practice. In the st place, when the filmed electrodes are made of pure metal (or metal containing nothing else but the impurities found in commercial grades, which impurities are lally silicon, titanium and iron, sometimes opper also), the efliciency of the rectifier is tow, especially when the electrolyte is hot, it isaptto be by reason of the losses due to the resistance encountered by the current. Also, the filmedmetal is subject to rapid corrosion due to the re eated break-down and re-formation of the film incident to the rectifying action. These drawbacks are to a considerable extent overcome by making 1e filmed electrodes of an alloy of alumium, magnesium andcopper, as described and claimed in my co ending application 9 ial No. 317,610, file November 6, 1928, t in the course of continued investigation ave found that aluminum alloyed with calcium, and preferably containing nickel also, is still better, as evidenced by longer life and by high efliciency even at boiling temperature. Advantageous results can be obtained with less, but I prefer to use at least about three per cent of calcium and two per cent of nickel. A like amount of copper may be used, but I consider nickel better. Of the latter element I may use as much as six per cent, and in some cases more, but I have not observed that the results are any better than with about 4 per cent. As for the calcium content I have not found that more than ten per cent offers any material advantage, but the invention is not limited to that amount since the alloy may contain calcium up to the maximum that can be alloyed with aluminum or with aluminum and nickel. Eight per cent of calcium is a good average amount, being satisfactory for impressed voltages exceeding 200 volts (R. M. S.) as well as for lower. Using an alloy composed of aluminum 88 per cent, calcium. 8 per cent, and nickel 4 per cent, approximately, with a condenser in parallel with the D. G. terminals of the rectifier, I have obtained an efiiciency of 69 per cent over long periods of time, even with the electrolyte boiling. At first the efiiciency may be ashigh as 88 per cent or higher. Instead of nickel I may use other meta s such as copper, cobalt, or silicon, but the electrical results are less advantageous. In general I may use any one or more of the metals nickel, copper, cobalt and silicon.

My experience indicates that an acid electrolyte, say one containing borax or sodium phosphate and boric or phosphoric acid gives substantially better results in the long run than a neutral or alkaline electrolyte, say one containing only borax or sodium hosphate or sodiumhydroxid. I prefer, owever, a solution containing one-half pound of anhydrous sodium tetraborate and one and a half pounds of boric acid per gallon of water. 95

For thenon-filming electrode carbon may be used, or any non-filming metal, preferably one which is not readlly deposited on the filming electrodes, as for example highsilicon iron, but I prefer graphite, as it resists well the chemical or electrochemical attack incident to the operation of the rectifier. The metal tank or vessel containing the electrol te may be used as the non-filmi electro e, as is common in the art.

11 the accompanying drawing,

1. 2, 3, 4 and 5 illustrate diagrammatically various forms ofelectrolytic rectifiers 'in'which my invention may be embodied.

Throughout the drawing, is a tank or vessel for the electrolyte, 11, 11 are filmed electrodes of aluminum-calcium-nickel alloy, 12 is a non-filming electrode of graphite, T is an auto-transformer or balance coil R, R are the terminals for the rectified output, one connected to the neutral point of the balance coil and the other to the anode, or anodes 12. A, A" are the input terminals for connection with a source of alternating voltage and current.

.. and onlythose which are imp needed. When both filmed In Fig. 1 the rectifier has one filming electrode and is therefore of the half-wave type, that is, (positive impulses impressed upon the filme electrode 11 are su presigd on e non-filming electrode 12 are passed. In Fi 2 and 3 two cells such as are shown in h ig. 1 are used for full-wave rectification, .111 the one case with the filmed electrodes connected to the transformer or bal' ance coil and in. the other with the nonelectrodes connected thereto. In Fig. 4 1 th filmedelectrodee are in the same vessel andonly one non-filming electrode is e ectrodes. are infthe same tank a balance .coil or transformer is necesesary, as ,in Fig. 4, for exand also in the arrangements shown in 2 and 3, in which only two halfwave cells are .used. With four or .more

such cells they may be connected as in Fig. 5,. in which case no balance coil or transformer is needed, though a transformer may helempl'oyed-as a convenient means for step- M p alternating voltage up assume' in or o The operation will be readily by tracin the course of the current in an of the gures. For e xample, ,ig. a an impulse coming in from A. Unable to pass through the termmpl thrgg t'cgnductoil' 13 to terminzll R, ltihenc; thr 1 e' trans atmg' evice not s own to terminals R, and from the lattenterininal to the non-film' electrode 12, the electrolyte, filmed. electro e 11, and thenceto the transformer T and out through terminal A. When the alternating. volta reverses the flow is from terminal A thro conductor 18, terminals R, B, unfilmed electrode 12 and filmed electrode 11 to terminal A. In Fig. ,5 an impulse comiig in at terminal A (me through unfilm electrode electrode 11' the current flows 12 in the lower tank at the right, filmed electrode 11 in the same tank, conductor 1 terminals R, R, conductor 15, unfilm electrode 12 in the upper tank at the left filmed electrode 11 in the same tank, an thence to terminal A. When the alternating volta e reverses, the current flows first through t e lower cell at the leftand out through the upper cell atjhe r' It is to be understood that e invention is not limited to the specific details herein described but can be carried out in other walys without departure from its spirit.

claim- 1. An electrolytic rectifier having an electrode made of an aluminum-calcium allo 2. An electrolytic rectifier having an 0 cctrode made of an aluminum-calcium alloy containin nickel.

3. An e ectrolytic rectifier having an electrode made of an aluminum-calcium alloy containin copper.

4. An e ectro ytic rectifier having an electrode made of an aluminum-calcium alloy having a calcium content not less than about 3 per cent.

5. An electrol ic rectifier having an electrode made 0 an aluminum-calcium alloy having a calcium content from 8 per cent to 10 per cent, a proximately.

6. An electro 'c rectifier having an electrode made 0 an aluminum-calcium allo containing not less than about 2 per cent 0 nickel.

7. An electrolytic rectifier having an electrode made of an aluminum-calcium alloy containing from about 2 percent to 6 r cent of nickel.

8. An electrolytic rectifier ha i" an electrode made of aluminum-calcium having a calcium content of from 8 to 10 per cent, approximately, and containing from about 2 to 6 per cent of nickel.

9. An electrol 'c rectifier hav' .an electrode made of uminum-calcium oy having a calcium content of about 8 cent and containing about 4 per cent 0 nickel.

10. An electrolytic rectifier havi an electrode made of aluminum-calcium y containing at least one other metal of the class consisting of nickel, cobalt, copper and sili- 11. An electrolytic rectifier com ri a filmed electrode composed of alumi huh i ab cium alloy, a non-filmin electrode, and an electrolyte in which sai electrodes are immersed, containing an acid of the clan of boric and phosphoric acids.

12. An electrolytic rectifier com a filmed electrode com of aluminumcalcium alloy, a nong electrode, and an electrolyte which said electrodes are immersed, containing born: and boric acid in solution.

13. An electrode for an electrolytic recti- 1,ooa,oso 3 10 signature.

RALPH D. MERSHON.

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