US2257728A

US2257728A - Rectifier

Info

Publication number: US2257728A
Application number: US266211A
Authority: US
Inventors: Willard H Bennett
Original assignee: SLAYTER ELECTRONIC CORP
Current assignee: SLAYTER ELECTRONIC Corp
Priority date: 1939-04-05
Filing date: 1939-04-05
Publication date: 1941-10-07
Anticipated expiration: 1958-10-07

Description

Oct. 7, 1941; w, H BENNETT 2,257,728I

' RECTIFIER Filed April 5, 1939 3 Sheets-smet 2 v INVENTOR. I 5 5554MB@ l ATTORNEY.

W. H. BENNETT oct. 7, 1941.

REGTIFIER .Filed April 5, 1939 3 Sheets-Sheet 3 4 HHH o uw 5 www aa ATTORNEY Patented Oct. 7, 1941 anormale Willard H. Bennett, Newark, Ohio, assignor to Slayter Electronic Corporation, a corporation of Ohio Application April 5, 1939, Serial No. 266,211

20 Claims.

My invention relates broadly to rectiers for delivering direct current `to a load from an alternating current source and employing electric emission apparatus operating at substantially atmospheric pressures.

One of the objects of my invention is to provide a system for rectlfying alternating current in which electric emission apparatus is employed at substantially atmospheric pressure for obtaining uni-directional current from alternating current under control of suitable bias potentials obtained from electric emission apparatus and wherein the controlling capacity for the emission apparatus is built directly into the electrodes of the emission apparatus.

Another object of my invention is to provide a construction of rectifier for alternating currents employing capacitive types of emitting elec-l trodes associated with control grid and target electrodes and in which the control grid electrodes are supplied with predetermined bias potential obtained from emission apparatus employing resistive emitting electrodes.

Still another object of my invention is to provide a circuit arrangement for a full wave rectier of the electric emission type including emitting electrodes, associated control grid and target electrodes and auxiliary rectiers including emitting electrodes and associated target electrodes and in which the emitting electrodes of the main rectifier are capacitively connected to the potential source by capacitive means built directly into the electrodes.

A further object of my invention is to provide a circuit arrangement for a full wave rectifier using capacitive emitting electrodes in association with target electrodes.

A still further object of my invention is to provide a construction of emitting electrode in which a multiplicity of emitting members are mounted in spaced relation in a mass of semiconductive or insulation material and potential applied `thereto through high potential means capacitively related to the central portions of the emit-tingV members fordischarge from opposite ends of the emitting members.

Another object of my invention is to provide a construction of high potential discharge electrode in which localized capacitive connection from a high potential source is established with get.

Still another object of my invention is to provide a construction of electric emitter formed by Cil Other and further objects of my invention re-` side in the construction of capacitive emitter and 'circuit arrangementtherefor in a rectification circuit as set `forthmore fully in the specication hereinafter following by reference to the accompanying drawings, in which:

Figure 1 is a transverse sectional view taken through a rectifier embodying my invention and showing the arrangement of capacitive double ended emitters, control grid and target electrodes; Fig; 2 is a vertical sectional view taken substantially on line 2'2 of Fig. l with certain of the elements partially shown in side elevation; Fig. 3 is a fragmentarysectional View taken substantially on line 3--3 of Fig. 1 with certain of the parts shown partially in elevation; Fig. 4 is a transverse sectional view through one of the capacitive double ended emitters of the main rec` tifier taken on line 4-4 of Fig. 2; Fig. 5 is a fragmentary vertical sectional view through the capacitive emitter of the main rectifier on line 5-5 of Fig. 4; Fig. 6 is a transverse sectional'view through the auxiliary rectier for developing the biasing components for the control grids of the main rectier; Fig. 7 is a vertical sectional View taken substantially on line 1-1 of Fig. 6 with 'certain of the elements illustrated in elevation; Fig, 8 is a fragmentary vertical sectional view taken on line 8 8 through the auxiliary rectier; Fig. 9 is a transverse sectional view through one of the double ended discharge electrodes of the auxiliary rectier taken substantially on line 9 9 of Fig. 7; Fig. 10 is a fragmentary vertical sectional View `of the double ended emitter of thel auxiliary rectifier taken substantially on line lll-I0 of Fig. 9; and Fig. 11 is a diagrammatic circuit arrangement of the rectication system of my invention employing capacitive electrodes.

My invention is directed to a rectiiication system particularly adapted for rectifying high voltage alternating currents and deriving direct stituted by double ended emitting electrodes and associated target electrodes and wherein connection is established between a high potential source and the double ended emitters by resistive means built directly into the structure of the electrodes. In the main rectier the double ended emitters are formed by a multiplicity yof double ended emitter members which extend in directions normal to a highp'otential bus which extends through a mass of semi-conductive or insulation material in which the double ended emitters are supported. The double ended emitters are capacitively related to the high potential bus by reason of the arrangement of an insulated sheath which is interposed between the high potential bus and the double ended emitters allowing controlled transfer of potential from the bus to the double ended emitters for discharge from opposite ends thereof to associated target electrodes. In the arrangement illustrated herein, the main rectier employs electrodes in which a tubular sheath of insulation material surrounds the high potential bus andY against which the double ended wire-like emitters establish substantially tangent contact. In the electrode structure for the auxiliary rectifier, a strip of insulation material is interposed between the high potential bus and the central portion of the doubleended emitters. The capacity between the high potential bus and the double ended emitters in the main rectiers 25 and 26 is substantially lumped and has been illustrated in the circuit diagram as a series capacity. The capacity, while electrically in series Vwith the emitters, is physically incorporated within .the electrode structure of the double ended emitters and has an action for controlling the discharge which is much more effective ,than if a capacity were externally used. in ser-ies with the bus as shown in Fig. 11. In the

auxiliary components

28, 29, 39, 3I, the insulating strip of material in the emitter I9 serves t0I allow current to pass from the bus to the double ended emitters only 'through the 'resistive material.

ln the circuit arrangement employing the capacity electrodes, the biasing components for the'control grids of the main rectifier are obtained from auxiliary rectifier units. The auxiliary rectier units have the emitters of one unit connected with one set of the control grid electrodes of one main rectifier while the target electrode of another unit of the `auxiliary rectiers is connected with the other setY of control grid electrodes of that main rectier, whereby one set of control grid electrodes# receives a positivey bias while the other set of control grid electrodes in each instanceVV receives a negative bias. Similarly the opposite portion of the main rectifier has one set of control electrodes therein connected to the emitters of a unit of the auxiliary rectifiers for receiving therefrom a positive bias, while the other set of control grid electrodes in the said main rectier unit is connected t the target ofAV another of the auxiliary rectifier units and receives therefrom a negative bias.

Both the main rectifier electrode assemblies and theY auxiliary rectifier electrode assemblies operate at substantially.atmospheric pressures.

i Referring tothe drawings in detail, reference characters I and 2 indicate the targets of the main rectier having associated therewith, rows of control members or

grid elements

3 and 4 and the emitting electrode assemblies shown generally at 5. The targets I and 2, control mem# bers or

grid elements

3 and 4, and the emitting electrode assemblies 5 are mounted in the spacial relationship shown by means of insulated supports 6 and 'I. The spacial'relationship of the component parts is such that with the potentials employed there is n0 possibility of sparking, arc- 'over, streamers, surging or incipient arc discharge between the components.

The emitting Velectrode assemblies 5 are constituted by a main high potential bus 'which is surrounded by insulating material 9'such as a tubular sheath of glass or other material. A multiplicity of parallel extending emitting members or wires I9 are arranged in uniformly spaced positions substantially tangential to the surface of ltubular sheath 9 and extending in directions normal to the axis of the bus 8. The emitting members or wires ID are embedded in a mass of semi-conducting or insulation material II which may be molded under pressure around theinsulated sheath 9 and around the emitting members or wires I0. The massof semi-conducting or insulation material II may be stream-lined from the central portion toward opposite edge portions from which the emitting members or wires I Il extend. The emitting members or wires I9 are double ended so that discharge occurs at each end thereof in the direction of targets I and 2. Transfer of energy from Vhigh potential bus 8 is effected through the capacity existing by reason of the insulated sheath 9 which surrounds high potential bus` 8. The emitting members or wires I0 which tangentially contact withthe surface of insulated sheath 9 as indicated at I2 in Figs. 1, 4 and 5, receive their energy from main bus 8 by a capacity transfer of energy from high potential bus 8.

The auxiliary, rectifier orrectier structure by which the required biasing components areY obtained for predetermining the potential of the lcontrol members or

grids

3 and 4 of the main rectifier has been shown in Figs. 6-10. The auxiliary rectifier comprises plate-like members constituting targets shown at I4 and I5. with intermediate conductive partitions illustrated at I6. The emitting electrode assemblies are shown generally at I'I comprising central bus I8 having a strip of insulation material I9 substantially coextensive therewith and embedded in a mass of semi-conductive material 20 in which there is supported a multiplicity of substantially parallel extending emitting members or wires 2I. The emitting members or wires 2I are uniformly spacedY along thelength of the electrode assembly I'I and extend in directions substantially normal to the axis of the bus I8. The insulated strip I9 has the surface thereof in contact With bus i8 at one side and in contact with emitting members or ,wires 29 at the opposite side. The insulated strip I9'serves as a dielectric in termediate the bus I8 and the emitting members or wires 2l. The transfer of current from bus E8 to emitting members or wires 2| is resistive and is regulated by the resistance of the material 29 between the bus and the emitting members. The mass of semi-conducting material 2i) is stream-lined or tapered from the central position 22 to the opposite edges from which the emitting members or wires 2I extend. The spacial relation of the emitting electrode assemblies I1 with respect to the targets I4 and I 5 and conductive partition members I6 is'maintained by means of end supports 23 and 24 formed of insulation material. The emitting members or wires 2| are double ended and discharge toward targets I4 and I5 and conductive partition I6.

In Fig. 11 I have shown a schematic wiring diagram for the rectiiier system of my invention employing the capacitive emitting electrodes in the main rectiiier and the resistive emittingelectrodes in the auxiliary rectifier. There are two sets of electrode assemblies constituting the main rectifier represented generally at 25 and 26.l The main rectifier 25 contains the targets I and 2, the control members or

grids

3 and 4 and the emitting electrode assembly 5, constructed and arranged as set forth in Figs. 15. The emitting electrode assembly includes the emitting members or Wires III associated in capacitive relation to the bus 8. In order to electrically represent the capacity in the circuit, I have indicated this capacity at 21. The main rectifier 25 contains a similar arrangement of electrodes to which I have applied the related reference characters I'-2 and 3'-4' designating the targets and control members or grids, respectively, and the emitting electrode assembly 5' including discharge members or Wires IIB' xcapacitively associated with bus 8 through a capacity which is the electrical equivalent of the capacity shown at 21'. While the capacities have been shown diagrammatically at 21 and 21', it will be understood that these capacities represent the inherent capacity within the emitting electrode assemblies between the emitting members or Wires ID-IIJ and the high potential buses 878'.

The auxiliary rectiers or rectifiers for securing the biasing components for the control mem,- bers or

grids

3 and 4 and 3' and 4' of the main rectifiers 25 andk 26 are shown generally at 28, 29, and 3|. Each of the sets of auxiliary rectiers includes emitting electrode and target assemblies of the type illustrated in Figs.

6-10. The emitting electrodes are shown at I1',

auxiliary discharge banks

28, 2,9, 30, 3| is maintained approximately `smooth by the

condensers

31, 38, 39, 40, respectively.

Alternating current to be rectified is supplied through primary winding 4I of transformer 42 to high potential secondary Winding 43. Terminal 44 of high potential secondary Winding ,4 3 connects to the high potential `bus 8 of the main rectier of emitting electrode assembly5 for. supplying energy to the emitter members II) through inherent capacity 21,. Terminal 44 also connects to emitting electrode assembly |1, of auxiliary rectifier 30 and tothe target |4"" of auxiliary rectifier 3|. The opposite terminal 45 of secondary Winding 43 .connects to bus 8' of emitting electrode assembly 5 of main rectifier 25 for supplying energy to 4emitter members I0' through inherent capacity 21. Terminal 45 also connects with the target I4 `of auxiliary rectifier assembly 28 and to the emitting electrode assembly I1 of auxiliary rectifier assembly 29 as shown.

`A separate auxiliar)r rectifier assembly is provided .for establishing a biasing potential' for each of the control members or grids 3 4 .and 3', 1|.` The auxiliary rectiers are so connected with the control members or grids that Control members or

grids

4 and 3 receive a. negative bias With respect to the associated emitting mem bers or wires I0 and I0 from auxiliary rectiflers 29 and 30, while control members or grids 3 and 4' receive a positive bias with respect to the associated emitting members or Wires I0 and I Il respectively from

auxiliary rectiiiers

28 and 3|. i

The rectier of my invention operates as a full wave rectifier with each of the main recti-` fier units 25, 26, functioning alternately to produce a positive discharge and a negative discharge. On the half of the alternating current cycle when terminal 44 is positive, there is a positive emission from the emitters I0 on the discharge electrode 5, directed to the target `2 by reason of the attractive negative bias .eiective on the control or grid element 4 at the same instant. Simultaneously, a negative emisfsion isy produced from discharge electrode 5' directed to target 2 by virtue of the attractive positive bias eiiective on the control or grid element 4' at 'the same instant. Current flows, therefore, from terminal 44 through rectier unit 25 from electrode 5 to target 2, through the conductor 41 to the load, and returns by conductor 46, rectiiier unit 2B from target 2 to electrode 5 and back to terminal 45. The different character of the emission in the rectifier units determines the direction of current Iiow `in. the `respective discharges.

When terminal is positive, like conditions prevail `but in displaced manner. Rectier unit 26 produces a positive discharge directed to target I', and unit 25 a negative discharge directed to target I, the control or grid elements 3' and 3 being respectively negative and 4positive at the same instant to control the discharge. The direction of current iiow through the load is the same as before, indicating that the system as a Whole produces full wave rectification. It Willbe noted however, that each of the rectifier units 25, 26, as connected, functions as -a full Wave rectifier only in cooperation with the other unit, in a series relation, one of the units producing a positive discharge in cooperation with a negative discharge produced in the other during any half cycle of operation.

The auxiliary rectifier units are half wave rectiiiers producing the required potentials in the proper sign, as noted on Fig. l1, and at the right time to produce the desired results. Thus, rectiers 28 and 39 are simultaneously operable when terminal 44 is negative and terminal 45 is positive, and rectiers 29 and 3| are operable on the other half of the cycle-the outputs of the auxiliary rectiiiers are not interconnected Y for full Wave rectification but are individually applied to the respective grid electrodes as bias potentials.

The rectified energy is delivered from targets I and 2 4of the main rectifiers to the negative side of the -load circuit as indicated at 4G. The opposite side of the load circuit extends from targets 2 and I through lead 41. A suitable filter represented generally by condenser 43 may be arranged across the output of the load circuit.

The discharge electrodes and associated targets of both the main rectiers and the auxiliary rectiers operate at substantially atmospheric pressures and Without the employment of re-lae 'tively expensive replaceable vacuum tubes. The 'main rectier units are relatively inexpensive in lconstruction and are readily replaceable at relatively low cost. I have described 'the emitting electrode assembliesas formed from resistive or insulating material in both the main rectiiier and'the auxiliary `rectiiier; in this connection I desire that Vit be understood that the plastic material from which the emitting electrode assemblies are formed may be rendered semiconductive by the addition of semi-conductive material such as graphite or lucite.

' I have described my invention in certain of its preferred embodiments, but I realize that changes may be made in the shape and form of the electrode assemblies and in the circuit arrangement in which such assemblies are employed and I desire that it be understood that no limitations upon my invention are intended Y other than may be imposed by the scope vof .the

interposed between said circuits comprising an emitting electrode and a target electrode, means forpsupporting said emitting electrode comprising a bus electrically connected with said input circuit, a multiplicity of discharge members and means for supporting said discharge members inacapacitive relation to said bus and directed toward said target electrode. v

3.' A 'rectifier comprising in combination, an alternating current input circuit, a direct current Voutput circuit, and an electrode assembly i interposed between said circuits comprising an emitting electrode and a target electrode, said emitting electrode comprising a bus electrically connected with said input circuit, an insulated sheath enclosing said bus, a multiplicity `of discharge members extending into surface contact with said sheath, and means for supporting said discharge members in uniformly spaced relation withV respect to said bus and along said sheath. 4, A rectifier comprising in combination, an electrode assembly comprising an emitting electrode, a control electrode and a target electrode, a high potential connection for said emitting electrode, a capacity interposed immediately between said emitting electrode and said high potential connection, input and output circuits associated with said electrodes, a source of alternating current connected with said input circuit and a rectifying device constituted by a target electrode and an auxiliary emitting electrode, and a connection between said auxiliary emitting electrode and one of the aforesaid electrodes whereby a portion of the alternating current is rectifiedv and impressed upon one of said rst mentioned electrodes. y 5.,A rectifier comprising in combination, an electrode assembly comprising an emitting electrode, a control electrode and a target electrode, a high potential connection forV said emitting electrode, a capacity interposedl immediately between said emitting electrode and said high potential connection,'input and output circuits associated with said electrodes, a source of alternating current connected with said input circuit and a rectifying device constituted by a target electrode and an auxiliary emitting electrode, anda connection between said auxiliary emitting electrode and said control electrode for impressing a bias potential on said control electrode.

6. Ina rectifying system, an electrode assembly comprising a doubleended discharge electrode, a pair of' target electrodes, control electrodes interposed between opposite ends of said discharge electrodes and said target electrodes, a high potential connection, a capacity interposed immediatelyV between said high potential connection andy said double ended discharge electrodes, input and output -circuitsassociated with A said electrodes, a source of alternating current connected with said input circuit, a pair of auxiliary rectifier assemblies interposed in circuit with said source, said auxiliary rectiers each including a target electrode and auxiliary emitting electrodes, a resistive connection tlo said auxiliary emitting electrodes, a connection through the resistive connection of one of the auxiliary rectifier assemblies and one of said control electrodes, and a connection from the target of the other auxiliary rectifier assembly to the other of said ,control electrodes.

7. A ull wave rectier system comprising a pair of rectiiier units, each consisting of double ended emitting electrodes, coacting control electrodes and associated target electrodes, high potential connections for said emitting electrodes, capacitive connections interposed between said high potential connections and said emitting electrodes, input and output circuits associated with said electrodes, said output circuit having terminals each connected with a target electrode in each of said rectifier units; a power source of alternating current, auxiliary rectier assemblies individual to each of said control electrodes and comprising a target electrode and an auxiliary emitting electrode, a connection from one control electrode of each of said rectifier units to the auxiliary emitting electrodes of certain of said auxiliary rectier assemblies, -connections between the targetY electrodes of said last mentioned auxiliary rectiiier assemblies and opposite sides of said alternating current source, connections from the target electrodes of others of said auxiliary rectier assemblies to the other control electrodes ofV said. full wave rectier units, and connections between the emitting electrodes of said last mentioned other auxiliary rectifier assemblies and opposite sides of said alternating current source. l

8. A full wave rectifier system comprising a pair of rectifier units, each including double ended emitting electrodes, coacting control electrodes and associated target electrodes, a high potential connection for each of said double ended emitting electrodes, a capacity immediately disposed between the said high potential connection and the double ended emitting electrodes, input and output circuits associated with said electrodes, saidoutput circuit havingterminals each connected with a target electrode in each of said rectifier units, a power source of alternating current connected with said input circuits and independent auxiliary rectifier assemblies individually connected with each of said control electrodes, said auxiliary rectifier assemblies Veachfincluding a target electrode, an auxiliary emitting electrode and a resistive connectionlto said auxiliaryl` emitting electrode, the auxiliary rectifier assemblies being connected in reverse position with respect to the control electrodes of each of said rectifier units.

9. A full wave rectifier system comprising a pair of rectier units, each including double ended emitting electrodes, coacting control electrodes and associated target electrodes, a high potential i connection for each `of said double ended emitting electrodes, a capacity immediately disposed between the said high potential connection and the double ended emitting electrodes, input and output circuits associated with saidelectrodes,4 said output circuit having terminals each connected with a target electrode in each of said rectifier units, a power source of alternating current connected with said input circuits and independent auxiliary rectifier assemblies individually connected with each of said control electrodes, said auxiliary rectifier assemblies each including a target electrode, an auxiliary emitting electrode and a resistive connection to said auxiliary emitting electrode, connections between a control electrode of each of said rectifier units and the resistive connections of separate auxiliary rectifier assemblies, connections between the target electrodes of other auxiliary rectier assemblies and the other control electrodes of the rectifier units, a connection from one side of said alternating current power source to the target and the resistive connection of the auxiliary rectifier assemblies associated with one of said rectifier units, and a connection between the opposite side of said alternating current power source and the target and the resistive connection of others of said auxiliary rectifier assemblies associated with the other of said rectifier units.

10. In a full wave rectifier system, a pair of rectifier units, each including double ended emitting electrodes, a capacitive connection to said double ended emitting electrodes, control electrodes associated with said double ended emitting electrodes, and target electrodes coacting with the double ended emitting electrodes of each of said rectifier units, input and output circuits associated with said electrodes, said output circuit having terminals e'ach connected with a target electrode in each of said rectier units, a source of alternating current connected with said input circuits, auxiliary rectier units interposed between said source of alternating current and the individual control electrodes of said rectifier units whereby opposite polarities are instantaneously impressed upon the control electrodes of each rectifier unit, and connections between opposite sides of said source of alternating current through the capacitive connections of the emitting electrodes of each of said rectiiier units.

11. An emitting electrode comprising a longitudinally extending high potential bus, a strip of insulation material coextensive with said high potential bus, a multiplicity of double ended emitting members extending in surface contact with said strip of insulation material in central spaced relation, and a mass of semi-conductive material for maintaining said double ended emitting members in surface contact with said insulation strip and for making electrical connection thereto from said high potential bus.

12. An emitting electrode comprising a longitudinally extending high potential bus, a strip uniformly spaced relation along said strip, andV a body of` semi-conductive material ern-bracing said-bus, said strip and said emitters for maintaining said -double ended emitters in resistive relation to said bus.

13.- An emitting electrode comprising a longitudinally extending high potential bus, a strip of insulation material coextensive with said bus and folded centrally thereof to partially embrace said bus,` a multiplicity of double ended emitters extending' in surface contact with said strip in uniformly' spaced relation along said 4stripg and means for maintaining said double ended emitters in resistive relation to said bus comprising a mass of semi-conductive material tapered from a relativelywide transverse dimension to a relatively narrow dimension adjacent the discharge ends of said double ended emitters.

14. An emitting electrode comprising a longitudinally extending high potential bus, a strip of insulation material coextensive with said bus and folded centrally thereof to partially embrace said bus, a multiplicity of double ended emitters extending in surface contact with said strip in uniformly spaced relation along said strip, and a mass of resistive material surrounding said double ended emitters and said bus and stream-lined from a central position toward the discharge ends of the double ended emitters.

15. An emitting electrode comprising a longitudinally extending high potential bus, an insulated sheath substantially enclosing said bus, a multiplicity of double ended discharge members establishing contact with one side of said insulated sheath, and means for maintaining said discharge members in uniformly spaced position in capacitive relation to said bus.

16. An emitting electrode comprising a longitudinally extending high potential bus, an insulated sheath substantially enclosing said bus, a multiplicity of double ended discharge members establishing contact with one side of said insulated sheath, and means for maintaining said discharge members in uniformly spaced position in capacitive' relation to said bus, said means being stream-lined from a central position toward opposite edges adjacent the discharge ends of said members.

1'7. A discharge electrode comprising a high potential bus, a tubular sheath of insulation material substantially enclosing said bus, a multiplicity of double ended discharge members establishing tangential connection with said tubular sheath at uniformly spaced intervals longitudinally thereof, and means for maintaining said double ended discharge members in capacitive relation to said high potential bus.

18. A discharge electrode comprising a high potential bus, a tubular sheath of insulation material substantially enclosing said bus, a multiplicity of double ended discharge members establishing tangential connection with said tubular sheath at uniformly spaced intervals longitudinally thereof, and means for maintaining said double ended discharge members in capacitive relation to said high potential bus, said means being tapered from a relatively wide central dimension toward opposite edges thereof adjacent the discharge ends of said double ended discharge members.

19. A discharge electrode comprising a high potential bus, atubular sheath of insulation maplicity of double ended discharge members establishing tangential connection with said tubular sheath at. uniformly spaced intervals longitudinallyvthereof, and means for maintaining said doubleV ended discharge members in capacitive relation to said high potential bus, said means comprising a molded mass of` plastic material stream-lined from a central position toward, opposite edges thereof adjacent the dischargeends of said Vdonhle ended discharge members.

d 20. A full wave rectication system vcomprising emitter and target means for alternately producingpositive and negative electric discharge l including separatetarget electrodes for the respective discharges, a duplicateoi said means, a.l load circuit, and means for supplying unidirec- S connected with said discharge means in opposite phase so that positive discharge in one of said means occurs simultaneously with negative disin the same direction.

WILLARD H. BENNETI.