US2576251A - Electrode spacer structure for electron discharge devices - Google Patents

Description

Nov. 27, 1951 L. E. CISNE 7 ELECTRODE SPACER STRUCTURE FOR ELECTRON DISCHARGE DEVICES Filed June 29, 1950 3 Sheets-Sheet 1 v MORNEY L. E. CISNE Nov. 27, 1951 ELECTRODE SPACER STRUCTURE FOR ELECTRON DISCHARGE DEVICES Filed June 29, 1950 3 Sheets-Sheet 2 INVENZ'OR L. E. C/SNE ATTORNEY L. E. CISNE ELECTRODE SPACER STRUCTURE FOR ELECTRON DISCHARGE DEVICES Nov. 27, 1951 s SheetsShet 3 Filed June 29, 1950 F IG. 6

INVENTOR L. E C/S/VE ATTORNEY Patented Nov. 27, 1951 ELECTRODE srAcEa STRUCTURE FOR ELECTRON mscmmcs DEVICES Luther E. Cisne, New Providence, N. J., assignor to Bell Telephone Laboratories, Incorporated, New York, N. Y., a corporation of New York Application June 29, 1950, Serial No. 171,111

16 Claims. (01. 318-268) This invention relates to electron discharge devices and particularly to such devices having precise interelectrode spacings.

In certain such electron discharge devices it is Y desirable to reduce the spacing between certain electrodes, such as the cathode and anode, or either of these and the control electrode, to a very minute distance in order to obtain favorable electrical characteristics. While this may possibly be done with accuracy in experimental models difliculty is encountered in specifying very small interelectrode spacings in commercialproduction because of the large dimensional tolerances that may be present in the commercially produced parts. Thus the close spacing axial electrodes are employed, other variations in the spacing being associated with the exactitude of the dimensions of the electrodes themselves.

'The total maximum deviation from the normal interelectrode spacing must be kept within a small enough percentage of the total spacing so that the electrical characteristics of the device will be substantially the same for devices with different deviations.

' As the maximum deviation is dependent on the support members and thus is constant regardless of the interelectrode spacing, this small percentage has been attained in the past by maintaining the total interelectrode spacinglarge. In order to be able to specify commercially a very small interelectrode spacing, it is necessary that the tolerances that might affect the interelectrode spacing be also maintained within very close limits. Thus it is necessary to reduce the maximum possible deviation to a minimum by providing a support structuie which introduces a minimum number of dimensional tolerances and in which the tolerances necessarily present and introduced by the support members can be held within very fine limits. This reduction in the number of dimensional tolerances introduced by the supporting members and in the size of the individual possible deviations reduces the maximum deviation in the spacing between the electrodes that must be anticipated in the commercially produced devices and thereby allows the specifying of a closer interelectrode spacing.

It is one general object of this invention to reduce the interelectrode spacings that may be attained in electron discharge devices.

Another object of this invention is to reduce the number of dimensional tolerances introduced by the support members mounting the electrodes and which must be added together to obtain the maximum deviation in the interelectrode spacing that must be anticipated.

A further object of this invention is to control within very close limits the deviation introduced by the dimensional tolerances of the support members.

A still further object of this invention is to provide an improved electrode mount for electron discharge devices that is easy to fabricate and assemble and which securely positions the electrodes both transversely and longitudinally.

These and other objects of this invention are achieved in one illustrative embodiment of this invention wherein coaxial cylindrical anode and cathode members are mounted by two crossed insulator mounting members which have stepped cut-out portions engaging the cathode and anode and supporting them, the cathode and anode being separated by a single critical dimension on each insulator which alone might introduce a dimensional deviation or eccentricity into the interelectrode spacing.

In one illustrative embodiment of this invention, the crossed mounting members are locked in position by end insulating spacer members which have crossed slits therein so that they fit onto the crossed insulators. The end spacers carry a plurality of conducting ears to which lead wires are connected to provide both support and electrical connections for the electrode aslead wires directly to spacers.

In still another illustrative embodiment of this invention, two coaxial cathodes and encompassing anodes may be positioned by a single base insulator mountingmember and individual sec- 0nd mounting members fitted onto the base mounting thereby providing crossed mounting members for each anode and cathode. A conducting plate fits into the base mounting member between the two electrode assemblies and serves as a shielding member. End insulating spacers having a plurality of conducting ears thereon may be provided to lock the mounting members and for connection to lead wires.

It is one feature of this invention that a plurality of electrodes be positioned by normally disposed insulating members having apertures therein against portions of which the electrodes bear,

these portions accurately positioning and supporting the electrodes.

It is another feature of this invention that an electrode system be supported by normally disposed planar insulating members having stepped portions therein to position the electrodes.

It is a further feature of this invention that the interelectrode spacing be determined by a single dimension on each mounting member, all of the defining elements of which dimensions may be determined at the same time in a single operation of a cutting tool, thereby allowing the electrodes to be positioned with a minimum of possible deviation or eccentricity in the interelectrode spacing.

It is a still further feature of this invention that .the crossed insulating mounting members may be locked spacer members having crossed slots therein into which the mounting members fit. These spacer members may be of a conducting material, in which case connections are made directly to them from the coaxial electrode system elements, or be of insulating material, in which case conducting means are supported thereby to which electrical connection may be made. In accordance with one feature of this invention, leads are secured to either the conducting spacers or the conducting means carried thereby to support the electrode system and mounting means and to provide electrical connection to external elements.

It is a still further feature of this invention that twin electrode assemblies may be mounted by normally disposed mounting members, one such member being common to the two assemblies, and each mounting member having an aperture with stepped portions to position the electrodes, the interelectrode spacing in each case being determined by a single dimension on each mounting member whereby the possible deviation or eccentricity in the interelectrode spacing is reduced to a minimum.

A complete understanding of this invention and of the various features thereof may be gained from consideration of the following detailed description and the accompanying drawing, in which:

Fig. 1 is a perspective view of an electron discharge device illustrative of one embodiment of this invention, portions of the vessel and various members having been broken away to show the internal elements of the device more clearly;

Fig. 2 is a sectional view of the coaxial electrode system and support mount of the embodiment of Fig. 1, one conducting ear being advanced in position and shown in section;

Fig. 3 is an exploded perspective view of the support mount and electrodes of the embodiment of Fig. 1;

Fig. 4 is a perspective view of an electrode system and support assembly illustrative of another embodiment of this invention, a portion of one of the spacer members having been broken away;

Fig. 5 is a perspective view of another embodiment illustrative of this invention comprising twin electrode assemblies, portions of various members having been broken away; and

Fig. 6 is a perspective view of a mountin 115 for the embodiment of Fig. 5. portions of the support mount and electrode assemblies having been broken away to show the mounting jig more clearly.

Referring now to the drawing, the illustrative embodiment shown in Fig. 1 comprises a vessel It which may ,be of glass, having an exhaust tubulation ii at one end and a plurality of leads extending through seals l6 in the base i9. In the embodiment illustrated five leads are employed,

' leads l2, l3, l5, and one which is not, visible providing electrical connections and support for the electrode elements. as further described below, and lead l4 providing a positioning guide for the proper mounting in a suitable tube socket. A getter support wire I6 and a getter |1 may be mounted by lead I! adjacent the top of the vessel It.

A cylindrical cathode 22, which may be of nickel, molybdenum, tungsten, or other known cathode material and may be coated with a suitable electron emitting material and a cylinder anode 24, which may advantageously be of nickel, tantalum, zirconium, or other known anode material, are supported'by two crossed insulator support or mounting members 26 and 21. The anode 24 is slightly shorter than the cathode 22 which it encompasses and with which it is coaxial. A heater 23, which may advantageously be a filament of tungsten, an iron-nickel alloy, or other known heater material, is placed within the cylindrical cathode 22.

The insulating mounting member 21 has an aperture 23 centrally therein, the aperture having two parallel sides with stepped portions 36 and 3| at each end, as best seen in Figs. 2 and 3. The member 21 further has a stepped outer ear 34 at each end. The distance between the stepped portion 3|! and the stepped portion 3| is the dimension 32, clearly seen in Fig. 2, which is of prime importance in controlling the accuracy of the spacing between the cathode 22 and the anode 24, as explained further below.

The insulating mounting member 26 has a similar aperture 36 centrally therein, the aperture having two parallel sides with stepped portions 31 and 38 at each end and an end slit 39 at each end. The distance between the stepped portions 31 and 38 is the dimension 40, clearly seen in Fig. 3, which dimension is also of prime importance in controlling the accuracy of the spacing between the cathode 22 and the anode 24, as explained further below. Mounting member 26 also has and ears 4| at each end. The mounting members 26 and 21 may advantageously be of mica or other planar insulating material.

The crossed insulating members 26 and 21 are locked in position by end insulating spacers 42 and 43, which may also advantageously be of mica or other planar insulating material. Spacer 42 is provided with crossed slits 44 and spacer 43 with crossed slits 45 through which the outer ears 34 and 4| of the mounting members 21 and 26 extend, as described more fully below.

As best seen in Figs. 2 and 3, when the electrode system and support mount are assembled, the cathode 22 is positioned against the stepped end portions 3| and 38 of the mounting members 21 and 26, respectively, and the anode 24 is positioned against the stepped end portions 30 and 31, the mounting members 21 and 26, respectively. The accuracy of the spacing between the anode and cathode is thus determined by the accuracy of the dimensions 32 and 40. In the assembling.

the same sign so that they add together.

awaaai the mounting member 25 is slid over the mounting member 21, the outer ears 34 extending through the end slits 39 and being positioned in place when the stepped portions of the outer cars 34 are against the end ears 4|. The end spacers 42 and 43 are then slid over the crossed mounting members 26 and 21, the end cars 34 and 4| extending through the slits 44 and 45.

The compact electrode assembly and support is positioned in the vessel H) by means of the leads |2, I3, I 5, and a fourth lead, not shown, and conductive ears 41 secured to each of the end spacers 42 and 43. Each conductive ear 41 is substantially L-shaped and has an aperture 48 therein along the base of the L, the material priorly positioned in the aperture being bent back to form a connecting surface 49 normal to the plane of the ear 41. The ears 41 are mounted by the end spacers 42 and 43 in pairs, being welded together as at 5.) through apertures in the spacers although the ears may be attached by other means as is known to the art. A pair of such cars 41 is provided for each lead on each end spacer making a total of sixteen such ears for the illustrative embodiment depicted in Fig. 1.

The leads l2, l3, l5, and the one not visible in the perspective view of Fig. I extend through the apertures 48 and are connected to the connecting surfaces 49 as by welding. The electrode assembly and support means are thus positioned by the encompassing leads secured to each end spacer.

Electrical connections are made from the. heater, anode, and cathode to the leads, the connections being made to one of the conductive ears on the inner side of the end spacers 42 and 43. Thus as shown in Fig. 1, one end of the heater filament 23 is connected to the lead |5 through the conductive car 41 to which it may be secured at the welded point 50. The other. end of the heater filament 23 may be electrically connected similarly to the lead in back in the perspective of Fig. 1 and not visible, while the anode 24 may be electrically connected through a tab 52 and a conductive ear 41 to the lead l2 and the cathode 22 may be electrically connected through a tab 53 and a conductive ear 41 to the lead i3.

Dimensional tolerances are usually introduced into an electron discharge device for each electrode separately and for each electrode positioning means. For this reason the determination of the spacing between any two electrodes is limited by the provision that must be made for the maximum possible pile-up of these dimensional tolerances, which will occur if each dimension deviates from the norm by its maximum allowable individual tolerance and all of these deviations are of When it is .desired to diminish the spacing between the anode and cathode of an electron discharge device to a very minute value, such as .004 inch or less, possible dimensional variations of 1-.0025 inch resulting from the total pile-up of tolerances effect a perceptible percentage change in the interelectrode spacing causing changes in the electrical characteristics of the device. In accordance with this invention, the maximum total eccentricity may be maintained as low as 1-.00025 inch or approximately one-tenth of that priorly attainable.

Referring again to the drawing, a single dimension controls the interelectrode spacing for each mounting member 21 and 26, namely, the dimensions 32 and 48. The steps 30 and 3| of mounting member 21 and the steps 31 and 38 of mounting member 25, and any additional steps that would be provided if other electrodes are employed between the anode and the cathode, can be formed at the same time on their respective mounting members so that all the steps of one aperture are formed at one time. Indeed, both apertures 29 and 36 may be formed by a single operation at the same time, the different end portions of the apertures, i. e., the slits 39, being formed in a second operation. Further not only is there but a single dimension which will introduce an eccentricity in the interelectrode spac ing, but that dimension may be very accurately controlled in a simple punching operation, when the mounting members are of mica. Close interelectrode spacing is thus made possible by the reduction of both the number of dimensional tolerances to introduce an eccentricity into the spacing and the tolerance of the single dimension controlling the spacing.

' Referring now to Fig. 4 there is shown one modification of the device illustrated in Fig. 1, wherein crossed mounting members 268 and 218 are locked in position by spacer members 55, 55, 51, and 58 of a conducting material, such as nickel. Each of the spacer members 55, 56, 51, and 58 has an aperture 6| centrally therein and an ear 59 integral therewith, the end of the ear being bent normal to the spacer member and comprising a surface 60 to which the leads l2. l3, l5, and the one not shown in Fig. 1 may be secured by welding. The ears 59 and surfaces 60 are positioned degrees apart so that each is secured to the proper lead. As the mounting members 268 and 218 are advantageously of the same width each of the spacer members 55, 55, 51, and 58 may be identical, the different spacer members being merely mounted at different angles. Electrical connections may be made from the elements of the coaxial electrode system directly to the spacer members by means of tabs. Thus one end of the heater filament 23 may advantageously be attached to a tab 63 carried by the mounting member 218, the tab being in turn secured to the spacer 55 and the other endof the heater filament 23 to a tab 64 carried by the mounting member 268, the tab being in turn secured to the spacer 58. Similarly, the cathode 22 may be connected to the spacer 56 by a tab 65 and the anode to the spacer 51 by a tab 66. The ears 53 may be secured to the leads by any desired lead orientation for ease in connection to the external circuits.

Referring now to Fig. 5 there is illustrated'another embodiment of this invention in which twin electrode assemblies are mounted and supported by insulator mounting members 21 and a base insulator mounting member 26 I, correspond- *ing to the insulator mounting member 26 in the embodiment of Fig. 1. Elements identical in this embodiment with that of Fig. 1 have been referred to by the same reference character. Thus the anode 24 and cathode 22 are supported in accurate coaxial relationship by the stepped end portions 38 and 3| of the apertures 29 in the mounting member 21, a minimum eccentricity that must be allowed for being attained because of the single dimension 32 positioning the two electrodes, whereby exceedingly close inter-electrode spacing may be achieved. Mounting member 26! is provided with two apertures 360 corresponding to the apertures 36- and identical therewith.

1c Mounting member 26| has a slit 58, best seen 7 in Fig. 6, approximately mid-way between the twin electrode assemblies. A metallic shielding member 69 extends through this slit and is positioned normal to the mounting member 26 l End insulating spacer members 420 and 43., correp in to end members 42 and 43 of the embodiment of Fig. 1, have crossedslits therein and fit over the crossed mounting members 21 and 2" to lock them in position. The shielding member 89 is also locked in position by tabs 10 extending through the spacer members 420 and 430 and bent over against their outer surfaces.

Pairs of conductive ears 410, "I, 412, 413, 414, and one not visible in the views illustrated, similar to the ears 41, are supported by the end spacer members 420 and 430. The twin-electrode assembly may be supported by these ears, each ear being secured to a separate lead as in a vessel similar to that illustrated in Fig. 1. Connections may be made from each element to an ear, the two heater filaments 23 being shown connected in parallel by strips 1i and 12, strip 12 being connected to ears 414 on end spacer member and strip 1| being connected to ears 412, shown partially in Fig. 6, on end spacer member 420. Similarly, one cathode member 22 may be connected to ears 410 as by a tab 530, a connection being made from its anode 24 to ears 413. Connections may be made from the other cathode 22 to ears 41! on end spacer member 420 and from other anode 24 to the ears on spacer member 43!! which are not visible in the perspective view illustrated in Fig. 5. Another pair of conductive ears may be secured to either end spacer 420 or 430 to provide connection from the external circuit to the shielding member 69 as may be desirable for certain circuit applications of this device.

Fig. 6 shows one mounting jig and assembling procedure for the twin-electrode assembly illustrated in Fig. 6, the principles however being equally applicable to the embodiment of Fig. 1. As shown there, a mounting jig or block 14 has a plurality of grooves 15 in one face, the grooves being shaped to receive the cathode and anode members 22 and 24. A central slit 16 is also provided in the face of the block 14 between the grooves 15. In assembling, the cathode 22, with the heater element 23 therein, is slid into the anode 24 and both members are positioned in aperture 29 in the mounting member 21. The mounting member is then slid into the groove 15, the cathode and anode being supported by the groove. When both mounting members 21 are in place, the mounting member 26! is dropped qver them, the stepped outer cars 34 of the mounting members 21 fitting in the slits 39 in mounting member 26!. The cathode and anode members 22 and 24 are then securely positioned in both apertures 36 in mounting member Ni and apertures 29 in mounting member 21 by the stepped end portions 30, 3|, 31 and 38, as described above. The metallic shielding member 69 is then placed in slit 68 in mounting member 26| and in slit 16 in the face of the block 14. The end spacer members 420 and 430, which advantageously have priorly had attached thereto the pairs of conductive ears 410, 41l, 412, 413, and 414, are then slid over the ends of the mounting members 21 and 2H and the tabs 10 on the metallic shield member 69, which tabs are then bent over against the face of the spacer end members. The block 14 advantageously has a depression opposite the bottom pairs of ears, such the spacer end members may be pressed against the sides of the block 14. Connections may then be made between the pairs of cars and thevarious electrode elements of the assembly.- The twin-electrode assembly and mounting members may be then removed from the jig 14 and lead wires slid into the apertures 48in the conductive ears, the leads being then secured, as by welding, to the conducting surface 49, as described above.

It is to be understood that the above-described arrangements are illustrative of the application of the principles of the invention. Numerous other arrangements may be devised by those skilled in the art without deviating from the spirit and the scope of the invention. Thus while the invention has been disclosed with reference to a diode, it is not limitedthereto but is also applicable to such devices employing more than two elements. Such other elements may take the form of control electrodes. screen electrodes, or suppressor electrodes as is known in the art for employment in affecting the electron discharge in such a device by externally applied voltages. Further while this invention has been illustrated by coaxial cylindrical anode and cathode members, the invention is not limited to the support and positioning of such particular electrode members or to their being of the form and configuration disclosed.

What is claimed is:

1. An electrode assembly for an electron discharge device comprising a pair of crossed insulator members positioned at right angles to each other, each of said members having an aperture therein along the line of intersection of said members, a plurality of electrodes positioned in said insulator members in said apertures, said electrodes bearing against portions of said apertures and being positioned thereby, and means locking said crossed insulator members.

2. An electrode assembly for an electron discharge device in accordance with claim 1 wherein said locking means comprises insulator end spacer members having crossed slits therein fitting onto said crossed insulator members.

3. An electrode assembly for an electron discharge device comprising a first electrode, a second electrode encompassing said first electrode and of shorter length than said first electrode, and a pair of crossed insulator mounting members, each of 1 said members having an aperture therein having stepped end portions, said electrodes being mounted in said apertures and separated by the distance between two stepped end portions in each aperture.

4. An electron discharge device comprising a plurality of electrodes, the outer electrodes encompassing the inner electrodes and being of shorter length than said inner electrodes, a pair of crossed insulator mounting members, each of said mounting members having an aperture therein, said apertures having stepped portions at each end, said electrodes fitting into said apertures and bearing against said stepped end portions, and means locking said members in position preventing motion of said electrodes or support members.

5. An electrode assembly for an electron discharge device comprising a cathode, an anode encompassing said cathode and of shorter length than said cathode, and a pair of crossed insulator mounting members, said members having each an aperture therein having stepped end portions, said cathode and anode being mounted in said as ears "I on spacer end member 420, so that 16 apertures and separated by the dimension beanode and said cathode, and means locking said crossed support members.

7. An electrode assembly for an electron discharge device in accordance with claim 6 wherein said locking means comprises insulator end spacer members having crossed slits therein and fitting onto said crossed support members.

8. An electrode assembly for an electron discharge device in accordance with claim 6 wherein said locking means comprises a plurality of metallic spacer members having slits therein and fitting onto said crossed support members.

9. An electron discharge device comprising a cathode, an encompassing anode of shorter length than said cathode, a first support member having an aperture therein, said aperture being stepped at each end and including a slit extending from each end, a second support member having an aperture therein, said aperture being stepped at each end, said second member fitting into the aperture and slit in said first member and being positioned normal thereto, said anode and cathode being positioned in said both apertures by said plurality of stepped ends, said cathode and anode being separated by the dimension between two stepped end portions in each aperture, and means locking said members in position preventing motion of said anode, cathode, or support members.

10. An electron discharge device comprising a vessel, a plurality oi. leads extending in said vessel, a hollow cathode, a heater element within said cathode, an anode of shorter length than said cathode encompassing said cathode, a pair of crossed mounting members each having an aperture therein, said apertures having stepped end portions engaging said anode and cathode, said mounting members being substantially normal to each other, insulating spacer members having slits therein fitting over said crossed mounting members and locking said mounting members, anode, and cathode in a compact electrode assembly, and a plurality of tabs positioned on said spacers electrically connected to said anode, cathode, and heater elements and secured to said leads.

11. An electron discharge device in accordance with claim 10 wherein said tabs are substantially L-shaped and have an aperture in the base of the L and a connecting surface adjacent said aperture and substantially normal to the plane of the tab, said tabs being mounted in pairs, one on each side of said insulating spacer members, and said leads extending through said apertures in said tabs and being secured to said connecting surfaces.

12. An electron discharge device comprising a vessel, a plurality of leads extending in said vessel. a hollow cathode, a heater element in said cathode, an anode encompassing said cathode and of shorter length than said cathode, a pair of crossed support members each having apertures therein, said apertures having stepped end portions mounting said anode 'and cathode. said anode and cathode being separated by the dimension between two stepped end portions in each aperture, a plurality oi metallic spacer members having slits fitting onto said crossed support members and locking said cathode, anode, and support members in position, means electrically connecting said anode, cathode, and each end or said heater element individually to one of said metallic spacer members, and means securing said metallic spacer members to said leads.

13. An electron discharge device in accordance with claim 12 wherein said last mentioned means comprises a tab integral with each oi. said metallic spacer members and including an end surface normal to said spacer member and secured to one of said leads, the tabs on said spacer members being angularly removed from each other. p a

14. An electrode assembly for an electron discharge device comprising a pair 01' cathodes, an anode encompassing each cathode and of shorter length than said encompassed cathode, a first base mounting member having a pair of apertures therein, said apertures being stepped at each end and each having a slit extending from each end, a pair of second mounting members having apertures therein, said apertures being stepped at each end, said second mounting members fitting into said slits in said first member, said anodes and cathodes being positioned by said stepped apertures, and means locking said mounting members in position substantially normal to each other preventing motion of said anodes, cathodes or mounting members.

15. An electron discharge device comprising a vessel, a plurality of leads extending in said vessel, a pair of hollow cathodes, a heater element in each cathode, an anode encompassing each cathode and or shorter length than said encompassed cathode, a first base mounting member having a pair of apertures therein, said apertures having stepped end portions and each having a slit extending from each end, a pair oi. second mounting members extending into said slits in said apertures and being substantially normal to said first base mounting member, said second mounting members each having an aperture therein, said apertures having stepped end portions, .said anodes and cathodes being positioned by said stepped end portions and being separated by the dimension between two stepped end portions in each aperture, insulator end spacers having slits therein, said spacers fitting over said first and second mounting members and locking said members, and a plurality of tabs positioned on said spacers electrically connected to said,

anodes, cathodes, and heater elements and secured to said leads.

16. An electron discharge device comprising a vessel, a plurality oi leads extending in said vessel, a pair of hollow cathodes, a heater element in each of said cathodes, an anode encom assing each of said cathodes and of shorter length than said encompassed cathode, a first base mounting member having a pair of apertures therein and a slit positioned between said a ertures, said apertures having ste ped end portions and each having a slit extending from said end, a pair of second mounting members extending into said second mentioned slits and said apertures and being substantiallv normal to said first base mounting member, said second mounting members each having an aperture therein. said apertures having step ed end portions, said anodes and cathodes bein mounted bv said ste ed end portions and being se arated b the dimension between t o step ed end port ons in each a erture, a shielding member extending into said first 11 mentioned slit between the two electrode assembliea, a pair of insulator end spacers having slits therein, one of said end spacers fitting onto each end of said crossed mounting members, means connecting said heater elements in parallel, and a plurality of tabs positioned on each of said spacers electrically connected to said cathodes, anodes, and parallel ends of said heater elements,

' said tabs being substantially L-shaped and each having an aperture in the base of the L and a connecting surface adjacent said aperture and substantially normal to the plate of the tab, said leads extending through said apertures in sai tabs and being secured to said connecting suraces.

LU'I'HER E. CISNE.

REFERENCES CITED UNITED STATES PATENTS Name Date Ewing Nov. 1, 1949 Number

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