US2032439A - Electric current rectifier - Google Patents

Description

March 3, 1936. s RUBEN ELECTRIC CURRENT RECTIFIER Filed April l5, 1955 INVENTOR g ONEY ATT SESS

Patented Mar. 3, 1936 UNITED STATES PATENT OFFICE ELECTRIC CURRENT BECTIFIER Application April 13, i933, Serial No. 665,869

9 Claims.

This invention relates to electric current rectiers and the like which employ asymmetric or unilateral conductive couples of the dry surfacecontact variety, the term "unilateral conductive couple as used hereinafter being intended to designate a device including an electrode element of a relatively electropositive material and another electrode element of a relatively electronegative material adapted to cooperate with the 10 former for the y electrochemical formation and maintenance at their junction of an inverse current-blocking nlm which has the property of conducting current in one direction and blocking current in the reverse direction.

General objects of the invention are the provision of such couples having improved characteristics, which are eiliclent, economical and readily manufactured, and have long service lives; the provision of an additional element in such couples which tends to prevent in operation'the formation of polarizing material of a character which reduces the emciency and shortens the service life; and structural embodiments of the device which are readily constructed and allow eiiicient use and operation thereof.

A specific object f the invention is the provision of such a couple provided with a layer of non-polarizing substance in contact with the material constituting the electronegative electrode element thereof to prevent the formation in operation of polarizing material adjacent the electronegative material, and to insure steadiness of output and increased eiliciency.

Anotherobject of the invention is the pro- 5 vision of such a unilateral conductive couple wherein the electropositive electrode element is composed of a relatively electropositive material formed from one of the elements chosen from an empirical group including beryllium, magnesiu 10 calcium, zinc and aluminum, or alloys or compounds thereof, and the other electrode element is composed of a relatively electronegative material, preferably including at least one compound of at least one of the elements sulphur, selenium,

5 and tellurium, the couple additionally being characterizaed by a layer of a non-polarizing substance interposed between the electronegative material and a terminal member.

A further object of the invention is the pro- .zo vision in such a unilateral conductive couple having an electropositive electrode of a silicon material having a high contact resistance with the electronegative electrode element and preferably formed from a silicide compound of 55 one of the elements chosen from an empirical Cal (Cl. F15-366) the elements sulphur, selenium and tellurium, of a 5 welded junction obtained by subjecting the electropositive and electronegative materials to a iiow of electric current to weld them together to form a physically and electrochemically stable unitary couple element.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises' the features of construction, combination of elements and arrangement of parts which will be exempli- 15 lied in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention reference should be had to 20 the following detailed description taken in connection with the accompanying drawing, in which:

Fig. 1 is a sectional schematic view of an elemental unilateral conductive couple of the dry surface-contact variety formed in accordance with the present invention;

Fig. 2 is a sectional view of one structural form of the device of the present invention utilizing couples of the type depicted in Fig. 1; a0

Fig. 3 is a sectional view of a structural ymodification on the device of the presentl invention;

Fig. 44 is a top plan view with parts in section and parts broken away of av further structural modification of the device of the present inven-` tion;

Fig. 5 is an end view of the device depicted in Fig. 4; and

Fig. 6 is a sectional view of one of the couple units of the structure depicted in Figs. 4 and 5. 40 p Prior to the present invention electric current rectiers and the like which employed asymmetric or unilateral conductive couples of the dry surface-contact variety have been provided with an essential contact resistance between the elec- 45 tropositive and electronegative electrode elements in a variety of Ways. These devices, at times, have been characterized by non-uniform operating characteristics, instability during operation under ordinary atmospheric conditions, and have had relatively short .service commercial lives. These and other undesirable characteristics are substantially avoided by the present invention.

In accordance with the present invention a device of this type is provided which has anr elecfrom a relatively electronegative material such as a metallic compound or mixture of compounds of elements chosen from an empirical group of elements of Sub-group B of the Sixth Periodic Group in-Mendelejeffs Periodic Table of Elements, for example, oxides, sulphides, selenides and tellurides. Some of the metallic elements from which it has been found suitable to form these compounds are copper, silver, cadmium, mercury, zirconium, lead, vanadium, arsenic, antimony, tantalum, bismuth, chromium, bolybdenum, tungsten, manganese and iron. Alloys of copper, such as brass, bronze and copper with vany of the elements zinc, silver, lead, tin antimony, etc., have also been found suitable from which to form the oxides, sulphides, selenides or tellurides. In addition, mixtures of the compounds, such as mixtures of oxides of various of the above mentioned metals, mixtures of sulphides and selenides or tellurides, and mixtures of one or more of such compounds with at least one metallic element such as cupric sulphide with a metal of the chromium group-all have been successfully used as electronegative electrode materials. The electronegative electrode element may consist of a mass of granular electronegative material or a solid body formed-in any suitable and well known manner.

In accordance with one modification of the present invention the electropositive electrode element is preferably formed from pure magnesium, the surface of which may be oxided in any suitable and well-known manner. The electronegative electrode element is preferably `formed from a sulphide of copper or an alloy thereof, such as, for example, brass. This element may be formed in the known manner of subjecting a metallic disc to the action of sulphur vapors or a sulphide of the metal may be formed, granulated and pressed into shape.

In accordance with another modification of the present invention, the electropositive electrode element may be formed from a silicon material, that is, silicon alone or -a compound of silicon and an element chosen from an empirical group of more electropositive elements of the electrochemical table of j elements preferably chosen from the Second and Third Groups of Mendelejels Periodic Table of Elements, comprising beryllium, magnesium, calcium, zinc and aluminum. This electropositive electrode element is placed in surface contact with an electronegative electrode element having a high contact resistance with the electropositive electrode element and `is preferably formed from, or provided with, a surface of' a compound of an element chosen from an empirical group of elements of Sub-Group B of the Sixth Periodic Group in Mendelejeffs Table of Elements, comprising sulphur, selenium and tellurium, or a ymixture of such compounds. The other constituents of the compound or compounds forming the electronegative material may be of any suitable metal or alloy thereof chosen from an empirical group of metals or materials comprising copper, silver, brass and bronzes.

The electropositive electrode element is preferably formed from granular magnesium silicide. The best mesh for such material has been found to be between about 36 and 60. With a finer mesh it has been found that the contact resistance is undesirably high and with a coarser mesh the resultant units are found to be undesirably leaky due to localized pressure. The electronegative electrode material in many instances is formed from granular cupric sulphide but a more preferable material is a mixture of cupric sulphide and cupric selenide of v about mesh. A suitable method of forming such a mixture is by adding about 20 percent selenium to the cupric sulphide vand then heat treating the mixture for a considerable period of time, for example, about three hours at about 250 C. in a vacuum to prevent oxidation and to volatilize any excess of sulphur and selenium.

With such electropositive and electronegative materials, it is necessary to use a structure which will confine these granular materials adjacenteach other with suiiicient pressure to insure good contact therebetween. This is readily accomplished by using a cup-shaped member in which the electropositive material in granular form is placed over a mass of the electronegative material.

`Any of the above described unilateral conductive couples are improved, in accordance with the present invention, by the use of a substance or substances tending to prevent, in operation, the formation of polarizing material adjacent the electronegative material. It has been observed, in the operation of certain couples, that a rather common progressive decrease in the output occurs with an attendant decrease in efficiency, which apparently is largely dependent upon the formation of an undesired layer of polarizing material adjacent the electronegative material. By providing a layer of non-polarizing substance adjacent the electronegative material in accordance with the present invention, it has been found that the service life of any greatly increased. 'I'his having been determined,

such couples are provided with such a layer of non-polarizing substance and may be efficiently operated at a substantially constant output for a greatly increased service life. Examples of some of the more desirable non-polarizing substances are aquadag, nickel, carbonized lead, alloys of nickel and chromium known under the trade name of nichrome", and conductive carbides of relatively low resistance such as tungsten carbide, tantalum carbide and chromium carbide.

A layer of non-polarizing substance is preferably provided in the assembly in the following manner. A carbonized nickel element is inserted adjacent the electro-negative material, preferably in the shape of a washer. This washer constitutes va sheet of nickel having a coating of carbon formed thereon. For the carbonized nickel may be substituted carbonized lead, that is a lead washer coated with carbon. Such an element is placed in the assembly with the carbonized side adjacent the electronegative material. When conductive carbidesI of relatively low resistance are used, discs are,y formed from pressed powders thereof. Wheat-.alloys of nickel and chromium known under the trade name of nichrome are carbon, graphite, tin, carbonized a of such couples may be used a nichrome material having a relatively v large amount of chromium is selected.

It has been found that thin sheets of brass containing about 20 per cent or more zinc may be used to prevent the formation of polarizing material adjacent the electro-negative electrode element provided that the rectifier assembly is kept under high pressure and the operating temperatures are kept below 150 C. Under such conditions these sheets of brass may be considered'to be layers of non-:polarizing material.

Referring to the drawing, Figs. 1 and 2 show structural embodiments of one form of the device ofthe present invention in which an elemental unilateral conductive couple of the dry surface-contact variety consists of an electropositive electrode element Il of any suitable electropositive material, such as, for example, aluminum, magnesium, or an alloy or amalgam thereof, etc. This electrode element is preferably in the form of a washer and lies in face engagement with the'electronegative electrode element Il of any suitable electronegative material, such as, cupric sulphide, or a sulphided brass body. A layer I2 of non-polarizing substance is placed in contact with the opposite face of the electronegative electrode element II. When these elements are in the form of washers they may be readily assembled as depicted in Fig. 2. Upon a bolt I3 provided with an insulating collar I4, and a pair of shoulder washers I5 and I6, is mounted a terminal plate I1 in face engagement with the electropositive electrode element I0 adjacent which is disposed the electronegative electrode element I I in face engagement with the layer of non-polarizing substance I2. 'Ihe layer I2 of non-polarizing substance engages another terminal plate I8 adjacent which is mounted another unilateral conductive couple, the non-polarizing layer I2 of which engages a third terminal plate I9. By the use of a bolt, means are provided for imposing pressure upon the elements to insure eil'lcient contact therebetween.

In Fig. 3 is shown a structural modification preferably used when the electropositive and electronegative materials are in granular form. A base member 29, preferably in the shape of a disc or square sheet formed from copper, is provided with a threaded shank 2I and a projecting portion 22 serving as a terminal member. On the face of the projecting portion 22 is preferably disposeda washer 23 of lead and a thin sheet of carbonized nickel 24. A collar 25 is positioned over the projecting portion 22 to cooperate with the lead washer. 23 and carbonized nickel element 24 and form a cup member having insulating walls 26 and a bottom provided with a layer of non-polarizing substance. The collar 25 may be formed from any suitable insulating material such as a vitrous enamel or magnesium silicate known to the trade as steatite and lavite, but is preferably formed from aluminum and coated on the inside with an insulating oxide layer 26.

A mass 21 of granular electronegativematerial, preferably a mixture of copper sulphide and copper selenide, particles of which are preferably of about 100 mesh, is placed in the collar 25 over the layer of non-polarizing substance 24. A mass of electropositive material, such as magnesium silicide in granular form, the particles of which are of a size which will pass through a screen of between about 36 mesh and 60 mesh, is positioned over the mass 21 of electronegative material within the collar 25. Another lead washer 23 is placed over the electropositive ma terial 2l with, if desired, an interposed element 24' of plain nickel yto prevent the grains of electropositive material from biting into -the relatively soft surface of the Alead washer 23 when pressure is applied. Another base member 26', having a threaded shank 2i and a projecting portion 22', serving as the other terminal member, Ais positioned as shown with the face of the projecting portion 22' in contact with the lead washer 23' within the collar 25. A resilient spider 29, having the arms thereof bowed as shown, is positioned over the shank 2l and bolts extending through holes in the arms of the spider 29 and the base members 29 and 20 complete the assembly. The bolts 30 are provided with suitable insulating, collars 3| to prevent short-circuiting of the asymmetric couple. An electrical terminal 32 is mounted upon the base member 29. The unit may be completed by mounting an additional electrical terminal 32 on the unit electrically connected with the base member 20' or, when these units are desired to be arranged in series, by coupling together shank ZI' with' the shank 2| of an adjacent unit by an internally'threaded collar 33.

In Fig. 4 is shown a structural modification of the device depicted in Fig. 3 with four unilateral conductive couples arranged to change alternating current to direct current. consists of a pair of base members 34 and 34', preferably of copper and provided with plugs or projecting-portions 35 and 35' adapted to serve as terminal members of the couple. Plugs 35 and 35' extend through the base members 34 and 34' respectively to form projections 36 and 36'. Adjacent couples have their base members 34', 34' electrically connected together by a metallic sleeve 31 which receives the projections 36', 36' as shown. Each couple is completed by a unit 38 which includes the electropositive and electronegative electrode elements, one of which is electrically connected to the plug 35 and the other of which is electrically connected to plug 35'.

'Ihe couples are preferably mounted in banks of two and secured together by bolts 39, 39, passing through end blocks 40, 4D, preferably of steel so'that the couples may be kept under desired pressure. The bolts 39, 39 may, if desired, pass through apertures in the base members 34, 34 since the latter are preferably made with a large surface area to act as efficient heatdissipating ns. In such case insulating sleeves 4I, 4I are mounted on the bolts 39, 39 to eliminate the possibility of the couples being short-circuited by the bolts 39, 39. ' I'he endsf'blocks 40, 40 are apertured to receive the projections 36, 36 and at least between one end block 40 and the adjacent base member 34 a shim 42 is mounted to allow the end block 40 to be resiliently stressed. The base members 34, 34 are provided with brackets 43, 43 to serve as supports and electrical connections.

As shown in Fig. 4, two banks are mounted side by side on metallic strips 44 and 45 which serve as electrical connectors between adjacent banks.

- The resultant structure is used to change alter nating current to direct current by connecting the alternating current terminals 46 and 41 to the metallic strips 44 and 45, the direct current being delivered from the assembly lby direct current terminals 48 and 49, one connected to avbase member 34' in one bank and the other connected to a base member 34' in the other bank.

The couple unit 38 depicted in Fig. 6 is generally similar to that depicted in Fig. 3. It in- Each couple cludes a. collar 50. of insulating material such as magnesium silicate commercially known as "steatite" and lavite surrounded by a metallic ring 5I preferably of brass adapted to strengthen the collar 50 and to serve as a heat dssipator. An additional feature of the unit 38 is the provision of a welded junction which increases the operating eilciency, avoids the necessity of a forming period when the unit is put in operation, and results in a unitary structure which can be readily handled. f

'I'he welded junction is preferably obtained by placing the collar 50 over a projecting electrode and inserting therein a lead washer 23, preierably about mils thick, a carbonized nickel disc 24, preferably about one mil thick, a small c amount of electronegative material, preferably a mixture of cupric sulphide and cupric selenide of about 100 mesh, a suitable amount of magnesium silicide, preferably between about 36 and 60 mesh, a nickel disc 24' and an additional lead washer 23' in the order set forth. A second electrode is brought into contact with the lead washer 2l',

pressure is applied, and current at a voltage and amperage greater than that at which the couple is designed to operate is allowed to flow between the electrodes from the electronegative material or anode side to the electrorespective material or cathode side. This flow of current is continued until the materials are welded together. As an example, welded junction couples designed to deliver about 5 amperes direct current at about 7 volts have been formed by placing them in a direct current circuit containing a variable resistance adjusted to allow about 50 amperes at about 12 volts to flow through the couple for periods of about 2 seconds each, these being repeated until the current flow was about 30 amperes. The resistance was then increased until the current flow was about 18 to 20 amperes and several 5-second periods of flow used until the voltage reached a. maximum. Obviously, however, the production of welded junctions is not dependent upon the method described.

'I'he use of at least one lead washer 23 adjacent the element 2l of non-polarizing substance is preferred in the assemblies since when suilicient pressure is applied to a couple unit the lead washer will be expanded to close completely the end of the collar 25 or 50 and seal oiit` from the atmosphere the relatively unstable electronegative material.` To insure eilicient sealing a second lead washer 23 is used adjacent the electrcpositive material as shown.

The pressure used in the formation of welded junctions not only insures good contact between the electropositive and electronegative materials to obtain an eflicient weld and formation of a current-blocking film but also expands the lead Washers to seal oil the electrode materials.

Pressure is additionally used in the completed assemblies to insure good contact between the adjacent surfaces of the elements, to allow the eflicient formation at the junctions between the electropositive material and the electronegative material of an inverse current-blocking lm when welded junctions are not used, to insure the maintenance of the current-blocking lm during the operation of the device, and to allow rapid dissipation of heat.

In the operation of the device depicted the electropositive material forms the cathode and the electronegative material forms the anode and, when current is passed between these electween. It is believed, but

practice of the particular 'mass of silicide of magnesium trode elements during the forming period, aneinverse current-blocking lm is formed therebeit is by no means certain that this current-blocking illmwhen the anode is of copper sulphide and the cathode is of magnesium silicide, is a sulphide of 'silicon and magnesium. I do not wish, however, to be bound by this theory with regard to the probable nature of the compounds comprising the inverse current-blocking nlm.

The use of the non-polarizing substance, such as carbon, apparently prevents in operation the formation 61' polarizing materialadjacent the v electronegative material which has been found progressively to decrease the output of the asymmetric or unilateral conductive `couple with av consequent decrease in efficiency and a relatively short service life.

It will thus be seen that the present invention t eiliciently attains the objects set forth above and provides asymmetric or unilateral conductive couples which are simple and rugged in structure land elllcient in operation, units including electropositive electrode elements oi' a silicide oi' magnesium and eiectroneg'ative electrode elements of an electronegative material including a sulphide of copper with which is associated a layer of a non-polarizing substance such as carbon having been operated continuously for periods greater than 1500 hours at a current density of about amperes per square inch and 10 volts potential per couple without any appreciable decrease in the outpu The use of the expression non-polarizing substances is intended to cover all substances of the type set forth above which have the property in unilateral conductive Vcouples of preventing the formation in operation-of materials adjacent the electronegative material which developduring operation and decrease the output of the couple.

Since certain changes may be made in the above construction and different embodiments of the invention could be made without departing from the scopey thereof, it is `intended that all matter contained in the above description or shown in the accompanying drawing shall be in.- terpreted as illustrative and not in a limiting sense. l

` Having described my invention, what I claim ias new and desire to secure by Letters Patent,

1. In electric current rectiflers and the like, of

relatively electronegative electrode element including a sulphide of copper in surface contact with said electropositive electrode, and a` nonpolarizing element of carbonized nickel in contact with said electronegative electrode element.

2. A unilateral conductive couple comprising a maintained in contact with an electronegative material including a sulphide of copper, and a layerof nonpolaiizing substance in contact with said electroneg'ative material.

3. A Vunilateral conductive couple comprising a mass of silicide of magnesium maintained in contact with a mixture of a sulphide of copper and a selenide of copper, and a non-polarizing element of carbonized nickel in contact with said mixture.

4. In electric current rectiers and the like, oi' the dry surface-contact variety, a unilateral conductive couple comprising a relatively electropositive electrode element formed from one of the materials beryllium, magnesium, calcium. zinc, aluminum, silicon and silicide, another electrode element having a surface of a relatively electronegative material of a compound of one of the elements sulphur, selenium and tellurium with one of the materials copper and copper alloys in surface-contact with said electropositive electrode and a non-polarizing element of carbonized nickel in contact with said electronegative electrode element.

5. In electric current rectiflers and the like of the dry surface-contact variety, a unilateral conductive couple comprising a relatively electropositive electrode element formed from one of the materials beryllium, magnesium, calcium, zinc, aluminum, silicon and silicide, another electrode element having a surface of a relatively electro- Inegative material of a compound of one of the elementsl sulphur, selenium and tellurium with one of the materials copper and copper alloys in surface contact with said electropositive electrode adapted to cooperate with the former for the electrochemical formation and maintenance of an inverse current-blocking iilm at their junction,`and a layer of non-polarizing carbon containing material in contact with said electronegative material.

6. In electric current rectiers and the like, of the dry surface-contact variety, a unilateral conductive couple comprising a relatively electropositive electrode element formed from one of the materials beryllium, magnesium, calcium, zinc, aluminum, silicon and silicide, another electrode elementxhaving a surface of a relatively electronegative material of a compound of one of the elements sulphur, selenium, and tellurium with one of the materials copper and copper alg loys in surface contact with said electropositive electrode adapted to cooperate with the former for the electrochemical formation and maintenance of an inverse current-blocking lm at their junction, and a non-polarizing element comprising a metal disc having a carbonized surface in contact with said electronegative material.

'1. In electric current rectifiers and the like, of

the dry surface-contact Variety. a unilateral conductive couple comprising a relatively electropositive electrode element formed from one of the materials beryllium, magnesium, calcium,

zinc, aluminum, silicon and silicide, another electrode element of a relatively electronegative material formed from a compound of -one of the elements sulphur, selenium and tellurium with one of the materials copper and copper alloys, said electronegative body adapted to cooperate with the electropositive body for the electrochemical formation and maintenance of an inverse current-blocking nlm at their junction, and a non-polarizing element in contact with said Aelectronegative electrode. said non-polarizing element comprising one of the substances aquadag, carbon, graphite. tin, carbonized nickel, carbonized lead, tungsten carbide, tantalum carbid chromium carbide and alloys of nickel and chromium in which the amount of chromium preponderat. L

8. In electric current rectifiers and the like, of the dry surface-contact variety, a unilateral conductive couple comprising a relatively electrof positive electrode element formed from one of the materials beryllimn, magnesium. calcium, zinc, aluminum, silicon and silicide, another electrode element of a relatively electronegative material formed from a compound of one of the elements sulphur, selenium and tellurium with one of the materials copper, brass and bronze, said electronegative body adapted to cooperate with the electropositive body for the electrochemical formation and maintenance of an inelectronegative element including a sulphide of copper in surface contact with said electropositive electrode and a non-polarizing element having a carbon surface in contact with said electronegative electrode element.

SAMUEL RUBEN.

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