US2939032A

US2939032A - Electron tube

Info

Publication number: US2939032A
Application number: US635004A
Authority: US
Inventors: Stanley R Jepson
Original assignee: Eitel Mccullough Inc
Current assignee: Varian Medical Systems Inc
Priority date: 1957-01-18
Filing date: 1957-01-18
Publication date: 1960-05-31
Anticipated expiration: 1977-05-31

Description

S. R. JEPSON ELECTRON TUBE May 31, 1960 Filed Jan. 18, 1957 56 INVENTOR.

StanIQY R Jcpson BY 7 'I v f ATTORNEY United States Patent ELECTRQN TUBE Stanley R. Jepson, Campbell, Calif., assignor to Eitel- McCullough, Inc., San Bruno, Califi, a corporation of California Filed Jan. 18, 1957, Ser. No. 635,004

Claims. (Cl. 313-256) This invention relates to electron tubes and particularly to electron tubes having electrode terminals in the form of coaxial conductive rings insulated from each other by ceramic.

At the higher frequencies (e.g. UHF and higher) it is desirable to use co-axial lines and resonant cavity circuits, with corresponding modifications in tube design to enable electrical connection to the electrodes thereof through coaxial terminals. For example, a tube designed for use in such high frequency circuits may comprise a plurality of ring-like electrode terminals arranged in co-axial array.

However, the fabrication of a tube having co-axial electrode terminals is not simple. In the first place, it is necessary that the various terminals be maintained in substantially perfect concentricity thus requiring a mechanically strong structure. Furthermore, difficulty has been experienced in selecting a material for use as an insulator between co-axial terminals. This is due to the fact that the insulator must be interposed between the terminal rings where it cannot be cooled, the terminal rings eifectively forming ovens containing such insulator. Thus insulators made of glass, for example, are heated to a comparatively high temperature during the operation of the tube and tend to break down both mechanically and electrically.

These problems may be diminished through the use of ceramic as the insulator between the terminal rings. Ceramic possesses greater mechanical strength than glass. Furthermore, ceramic may be heated to a higher temperature without impairing its mechanical or electrical characteristics. However, ceramic structures have been more expensive to fabricate. This is due to the fact that the ceramic pants are rigid and are not subject to being molded or otherwise formed during the fabrication of the tube, as is glass. Instead the ceramic parts are accurately formed within very close tolerances prior to being assembled into the tube and the hermetic seals between the ceramic parts and metal parts of the tube are made after such assembly. In addition, the differential in thermal coefficient of expansion between the metals and ceramics has complicated the design of electron tubes utilizing ceramics since it tends to make seals between such metals and ceramics unreliable.

It is an object of this invention to provide an improved electron tube utilizing ceramic which issimple and inexpensive to fabricate.

It is a further object of the invention to provide an improved electron tube possessing increased mechanical strength throughout a greater temperature range. 7 It is yet another object of this invention to provide an electron tube having an improved arrangement of coaxial electrode terminals insulated from each other by ceramic.

Briefly an electron tube according to one embodiment of this invention comprises a metallic electrode terminal member having a flat surface, a ceramic member mounted on a portion of the flat surface ofthe metallic terminal 2,939,032 Patented May 31, 1960 ICC member, and a ceramic ring surrounding the ceramic member and having one end hermetically sealed to the flat surface of the metallic terminal member. The ceramic member has a metallic coating on the exterior surface thereof and an electrode is mounted on the ceramic member opposite from the metallic member, the metallic coating electrically connecting the electrode and the metallic terminal member. The ceramic ring may have a metallic ring hermetically sealed to the outer surface of the end thereof opposite from the metallic member, the metallic ring being insulated from the metallic member by the ceramic ring.

.The invention possesses other objects and features of advantage, some of which, with the foregoing, will be set forth in the following description of the invention. It is to be understood that the invention is not limited to the disclosed species, as variant embodiments thereof are contemplated and may be adopted within the scope of the claims.

The invention will be more completely described hereinafter with reference to the attached single sheet of drawing wherein the figure is a view partially in elevation and partially in cross-section of an electron tube embodying this invention.

Referring to the figure, a tube embodying this invention may be any type of tube having co-axial electrode terminals as illustrated. It should be understood that, although the tube 10 chosen for illustration is a tetrode having cylindrical electrodes, this invention is not limited to use in tetrodes or in tubes having cylindrical electrodes, but would be equally applicable to a mode having planar electrodes, for example, as Well as to tubes employing velocity modulation such as klystrons or traveling wave tubes.

As shown in the figure, an indirectly heated cathode 12 is located at the' center of the tube 10. A cylindrical control electrode 14 surrounds the cathode 12 and a cylindrical screen electrode 16 surrounds the control elec trode 14. An inverted cup-shaped anode 18 surrounds the screen electrode 16 and forms a part of the tube envelope. The open end of the anode 18 is provided with an outwardly extending flange 20 to which one end of an insulating ring 22 (which may be glass, for example) is hermetically sealed. A metallic terminal ring 24 is hermetically sealed to the opposite end of the insulating ring 22 from the anode 18. A disk 28 having a central aperture and made of insulating material such as glass is hermetically sealed within the terminal ring 24 by means of a sealing ring 26. The screen electrode 16 is supported on and electrically connected to such terminal ring 24 and sealing ring 26 by means of hollow

metallic skirts

30 and 32. A metallic support cylinder 34 is hermetically sealed through the central aperture in the insulating disk 28. The control electrode 14 is mounted on and electrically connected to the inwardly extending end of the support cylinder 34 by a hollow metallic skirt 35, the other end of the support cylinder 34 serving as an electrical terminal for the control electrode 14. The cathode-heater assembly 36 extends through the control electrode support cylinder 34 and within the control electrode 14 and is hermetically sealed to the control electrode support cylinder 34 by means of a sealing ring 38, thus completing the vacuum tight envelope of the tube 10. The envelope of the tube 10 may be evacuated through an exhaust tribulation 39 provided on the anode 18, for example, which may be sealed as shown when such evacuation is complete.

The cathode 12 is cup-shaped, the open end thereof being supported on one end of a heat dam cylinder 40 made of thin metal foil. The electron emissive portion of the cathode comprises a coating of therm'ionically emissive material on the exterior sidewall 42 of the cupshaped cathode 12. A filamentary heater 44 is mounted within the cup-shaped cathode 12.

-'According to this embodiment of the invention, the lower end of the heat dam cylinder 40 is brazed or otherwise attached to a reinforcingring 46. The reinforcing ring is provided with a flange 48 extending inwardly thereof.

One end of a first ceramic ring 50 is brazed or otherwise rigidly attached to the lower surface of the flange 48. An annular metallic member '52 is hermetically sealed as by brazing to the other end of the first ceramic ring 50 and extends outwardly from such ceramic ring 50.

The exterior sidewall of the first ceramic ring 50 is provided with a metallic coating 54 which electrically connects the reinforcing ring 46, and thus the cathode 12, to the annular metallic member 52. The annular metallic member 52 is provided with a downwardly extending cylindrical portion 56 to serve as an electrical terminal for the cathode 12.

A second ceramic ring 58 surrounds the first ceramic ring 50 and is in co-axial relationship therewith. One end of the second ceramic ring 58 is hermetically sealed as by brazing to the portion of the annular metallic member 52 which extends outwardly from the first ceramic ring 50.

The metallic sealing ring 38 is hermetically sealed to the opposite end of the second ceramic ring 58 from the annular metallic member '52, the second ceramic ring 58 insulating the sealing ring 38 from the cathode-heater assembly.

The'filamentary heater 44 is supported within the cupshaped cathode 12 by means of a center support rod 60 extending co-axially within the cathode-heater assembly 36. The center support rod 60 is supported on the inner surface of the first ceramic ring 50 by means of a plurality of support rings 62. The support rings 62 are positioned along and brazed to the support rod 60 and extend between the inner surface of the first ceramic ring 50 and the support rod 60. At least one of the support rings 62 is hermetically sealed about its outer periphery to the inner surface of the first ceramic ring 50. It will be seen that the support rod is thus supported by the support rings 62 at a plurality of points spaced along its axis, thereby insuring the co-axial alignment of the support rod 60 with the cathode-heater assembly 36 and the rigid maintenance of such alignment.

One end of the filamentary heater is attached to the inwardly extending end of the center support rod 60, the heater 44 spiraling downwardly about the end portion of the support rod 60. The other end of the heater 44 is electrically connected to the cathode 12 by means of a support post 64 brazed or otherwise rigidly attached to the upper surface of the flange 48 on the reinforcing ring 46 and extending upwardly within the cathode 12. Thus, the lower end of the center support rod 60 serves as one terminal for the heater 44, the other terminal for the heater 44 being the cathode terminal 56.

As shown in the figure a pair of insulating disks 66 may be provided within the cathode 12 to act as heat shields and to prevent excessive vibration of the heater 44. The disks 66 are provided with apertures through which the center support rod 60 and the support post 64 pass. The disks are mounted on the center support rod 66 and support post 64 by means of wires 68 which pass through other apertures in the disks and are brazed at both ends to rod 60 or post 64. The outer peripheries of the disks 66 are in close-spaced relation to the inner surface of the heat dam cylinder 40 and tend to prevent excessive vibration of the rod 60, post 64 and heater 44.

In the fabrication of the cathode-heater assembly according to this embodiment of the invention the first step is to metalize the proper portions of the surfaces of the ceramic rings 50 and 58. Such metalizing may be accomplished, for example, by painting such surface por tions of the ceramic rings 50 and 58 with a paint comprising metallic particles suspended in a volatile binder. For example, a mixture of molybdenum, manganese, and titanium powders suspended in a nitrocellulose binder may be used. The ceramic rings 50 and 58 are then subjected to heat treatment to volatilize the binder and sinter the metallic powders to the desired areas thereof.

According to this invention, the entire outer surface including the ends, and a small strip about an inner circumference spaced from such ends of the first ceramic ring 50 are provided with metallic coatings as described above. Similarly one of the ends and a portion of the outer surface at the other end of the second ceramic ring 5 8 are provided with metallic coatings. The thickness of the metallic coating 54 on the outer surface and ends of the first ceramic ring 56 has been exaggerated in the figure in order to clearly show the electrical connection between the annular metallic member 52 and the reinforcing ring 46. In actuality the metallic coating is too thin to be shown in cross-section and noretlort has been made to show the inner metallic coating on the first ceramic ring 50 or the metallic coatings on the second ceramic ring 58 which serve solely as part of the hermetic seals made to the ceramic rings 50 and 58.

The second ceramic ring 58 is then forced into the sealing ring 38, the sealing ring '38 having an end portion 70 of slightly smaller internal diameter than the external diameter of the ceramic ring 58, such that the end portion of the ceramic ring 58 having the metallic coating on the outer surface thereof is placed under compression. Thus, when a hermetic seal is later made between the ceramic ring 58 and the sealing ring 38, the strain in the rings 38 and 58 will tend to compensate for the differential in thermal expansion thereof. Furthermore, the tolerance in dimensions of the parts will tend to be less strict due to the press fit therebetween.

The support rings 62 are then brazed to the center support rod 60, preferably in the orientation shown. Similarly, the annular metallic member 52 is brazed to one end of the cathode terminal cylinder 56 in co-axial relation thereto, as shown. It should be understood that the metal-to-metal brazes described above are gas tight and that they have a higher melting temperature than the metal-to-ceramic brazes to be described hereinafter.

The various parts are then placed in a brazing jig (not shown) made of carbon or other material which is not wet by the metal-to-ceramic brazing material and which may comprise a member provided with a plurality of concentric circular grooves and a central circular recess each of a diameter corresponding to the part to be positioned thereby and of selected depth. The cathode terminal member 56 and attached annular metallic member 52 are placed in the jig such that the lower end of the terminal member is received in and aligned by the circular groove adjacent the central recess. Similarly the center support rod 60 is placed in the jig suchthat it is supported in a vertical position and in co-axial alignment with the cathode terminal 56 by the engagement of the lower end thereof with the central recess in the jig.

A piece of wire (not shown) made of metal-to-ceramic brazing material is then wrapped around the center support rod to form a ring supported within the channel formed by the lower supporting ring '62 and the next adjacent supporting ring 62. A flat washer (not shown) made of metal-to-ceramic brazing material is placed on the upper surface of the annular metallic member. The above mentioned metal-to-ceramic'brazing material may be any suitable material, but is preferably copper-silver eutectic which has superior flowing properties when molten.

The first ceramic ring 50 is then positioned about the center support rod 60 such that the strip of metallic coating on the inner surface thereof is in alignment with the outer periphery of the lower support ring 62, the ring 50 being supported at its lower end on the annular metallic' member 52 with the Washer of brazing material therebetween. It will be seen that co-axial alignment of the member 52 is obtained by engagement of its inner periphery with the support rings 62. Similarly the second ceramic ring 58 and the sealing ring 38 into which it is press fit are positioned in the jig with the lower end of the second ceramic ring 58 in contact with the washer of brazing material on the annular metallic member 52 and the lower end of the sealing ring 38 in engagement with another circular groove in the jig to insure the coaxial arrangement thereof with the other parts of the assembly. A ring or washer (not shown) of ceramic-tometal brazing material (e.g. copper-silver eutectic) is placed on the upper end of the second ceramic ring 58 in position to flow between such ring 58 and the sealing ring 38 at brazing temperature. Similarly a fiat Washer (not shown) of ceramic-to-metal brazing material is placed on the upper end of the first ceramic ring 50. The reinforcing ring 46 is then placed on the upper end of the first ceramic ring 50 with the lower surface of the inwardly extending flange 48 thereof in contact with the washer of brazing material. A cap (not shown) made of the same material as is the rest of the jig is placed over "the reinforcing ring 48 and contacts both the outer surface of the reinforcing ring 46 and the outer surface of the first ceramic ring 50 to secure co-axial alignment thereof. A hole is provided in such cap through which the support post 64 is inserted and by which the support post 64 is held in an upright position with the lower end thereof in contact with the upper surface of the inwardly extending flange 48 of the reinforcing ring 46. A drop of brazing material, which may be the same as the metal to-ceramic brazing material, is attached to the lower end of the support post 64 to bond it to the reinforcing ring. The cap is also provided with a centrally located hole through which the center support rod 60 projects.

The jig with the assembled parts is then placed in an oven and heated to brazing temperature. The brazing material melts and flows between the parts to be brazed thus accomplishing all of the brazes simultaneously. The assembly is allowed to cool and is then ready for the attachment of the insulating disks 66, the heater 44, and the previously assembled cathode 12 and heat dam cylinder 40 in that order. After such attachment the completed heater-cathode assembly 36 may be assembled with the remaining portions of the tube, the sealing ring 38 being arc welded at its lower end to the grid support cylinder 34 to provide a hermetic seal therebetween.

Due to the simplicity of fabrication and to the inexpensive methods made possible thereby a tube embodying this invention is adapted for high production techniques. Furthermore, the mechanical and electrical characteristics of a tube embodying this invention represent a substantial improvement over the prior art and make possible many new applications thereof particularly when dependability and ruggedness are required.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is: i 1. An electron tube having a plurality of electrodes, including a cathode and an anode, said tube comprising a metallic electrode terminal member having a flat surface, a ceramic member mounted on one portion of said flat surface of said metallic member, and a ceramic ring surrounding said ceramic member and having one end hermetically sealed. to another portion of the same fiat surface of said metallic member, one of said plurality of electrodes being mounted on said ceramic member, and a metallic coating on a surface of said ceramic member electrically connecting said electrode to said metallic member.

2. An electron tube comprising a plurality of electrodes, including a cathode and an anode contained within anlev'acuated envelope, said envelope comprising a meiallic electrode terminal member having two oppositely disposed major surfaces, a ceramic ring, one end of said ceramic ring being hermetically sealed to one of said major surfaces of said metallic member, and a metallic ring hermetically sealed to the opposite end of said ceramic ring from said metallic member, a ceramic member mounted on said metallic member within said ceramic ring, said ceramic ring and said ceramic member being in nonabutting relationship, and on the same one of said major surfaces of said metallic member and on flat portions of said major surface one of said plurality of electrodes being mounted on said ceramic member, and a metallic coating on a surface of said ceramic member electrically connecting said one electrode to said metallic member.

3. An electron tube comprising a plurality of electrodes, including a cathode and an anode contained within an evacuated envelope, said envelope comprising a metallic electrode terminal member having a flat surface, a first ceramic ring, one end of said first ceramic ring being hermetically sealed to a portion of said flat surface of said metallic member, a second ceramic ring surrounding said first ceramic ring and having one end hermetically sealed to another portion of the same flat surface of said metallic member, and a metal ring hermetically sealed to said second ceramic ring at the end thereof opposite from said metallic member, one of said plurality of electrodes being mounted on said first ceramic ring, and a metallic coating on a surface of said first ceramic ring electrically connecting said electrode to said metallic member.

4. An electron tube comprising a plurality of electrodes, including a cathode and an anode contained within an evacuated envelope, said envelope comprising an annular metallic electrode terminal member having a flat surface, a first ceramic ring, one end of said first ceramic ring being hermetically sealed to a portion of said flat surface of said annular metallic member, a second ceramic ring surrounding said first ceramic ring and having one end hermetically sealed to another portion of the same fiat surface of said annular metallic member, said ceramic rings being in co-axial relationship to each other, an elongated support rod extending co-axially within said ceramic rings and said metallic member, and a metallic ring having its inner periphery hermetically sealed to said support rod and its outer periphery hermetically sealed to a circumferential portion of the inner surface of said first ceramic ring, one of said plurality of electrodes being mounted on said first ceramic ring, and a metallic coating on the outer surface of said first ceramic ring electrically connecting said one electrode and said metallic member.

5. An electron tube comprising a plurality of electrodes, including a cathode and an anode contained within an evacuated envelope, said envelope comprising a hollow cylindrical metallic member having a fiat radially extending surface, a first ceramic ring having one end hermetically sealed to said radially extending surface of said metallic member, a second ceramic ring surrounding said first ceramic ring in spaced relation thereto and having one end hermetically sealed to the same radially extending surface of said metallic member, said ceramic rings being in co-axial relationship to each other and to said metallic member, an elongated metallic rod extending co-axially through said metallic member and said ceramic rings, a hermetic seal between said rod and the inner surface of said first ceramic ring, and a metallic ring hermetically sealed to the end portion of said second ceramic ring opposite from said metallic member, said metallic ring being co-axial with said rod and with said cylindrical metallic member.

6. An electron tube comprising a plurality of electrodes, including a cathode and an anode contained Within an evacuated envelope, said envelope comprising a hollow cylindrical metallic electrode terminal member having a fiat radially extending surface, a first ceramic ring, one end of said first ceramic ring being hermetically sealed to a portion of said flat surface of said annular metallic member, a second ceramic ring surrounding said first ceramic ring and having one end hermetically sealed to another portion of the same flat surface of said annular metallic member, said ceramic rings being in coaxial relationship to each other, an elongated rod extending co-axially through said ceramic ring and said metallic member, a metallic ring extending radially outward from the outer surface of said rod to the inner surface of said first ceramic ring, said metallic ring being spaced from the ends of said' rod and said first ceramic ring and being hermetically sealed to the outer surface of said rod and the inner surface of said first ceramic ring, and a metallic terminal ring hermetically sealed to the end portion of said second ceramic ring opposite from said annular metallic member, a first one of said plurality of electrodes being mounted on said first ceramic ring, a metallic coating on the outer surface of said first ceramic ring electrically connecting said first electrode to said cylindrical metallic terminal member, and a second one of said plurality of electrodes mounted on and electrically connected to said metallic terminal ring.

7. An electron tube having a plurality of electrodes, including a cathode and an anode, said tube comprising an envelope, said envelope comprising a hollow cylindrical metallic member having a flat radially extending surface, a first ceramic ring having one end hermetically sealed to said radially extending surface of said metallic member, said first ceramic ring having a metallic coating on the outer surface thereof electrically connected to said metallic member, a second ceramic ring surrounding said first ceramic ring in spaced relation thereto and having one end hermetically sealed to the same radially extending surface of said metallic member, said ceramic rings being in co-axial relationship to each other and to said metallic member, an elongated metallic rod extending co-axially within said metallic member and through said ceramicrings, and a hermetic seal between said rod and the inner surface of said first ceramic ring, and a filament mounted on said rod, one end of said filament being electrically connected to said rod and the other end of said filament being electrically connected to said metallic coating on said first ceramic ring.

'8. An electron tube having a plurality of electrodes, including a cathode and an anode, said tube comprising an envelope, said envelope comprising a first hollow cylindrical metallic member having a flat radially extending surface, a first ceramic ring having one end hermetically sealed to a portion of said radial surface of said metallic member, said first ceramic ring having a metallic coating on the outer surface thereof electrically connected to said metallic member, a second ceramic ring surrounding said first ceramic ring and having one end hermetically sealed to another portion of the same radially extending surface, said rings being in co-axial relationship to each other and to said metallic member, an elongated metallic rod extending co-axially within said metallic member and through said ceramic rings, a hermetic seal between said rod and the inner surface of said first ceramic ring, and a metallic ring surrounding said second ceramic ring and a portion of said metallic member, said metallic cylinder having a restricted portion hermetically sealed to the end portion of said second ceramic member opposite from said cylindrical metallic member, a filament mounted on said rod, one end of said filament being electrically connected to said rod and the other end of said filament being electrically connected to said metallic coating on said first ceramic member, one of said plurality of electrodes being electrically connected to said metallic ring whereby said metallic ring, said metallic cylinder and said metallic rod may serve as electrical terminals for said tube.

9. An electron tube comprising a plurality of electrodes including a cathode, an anode, and a filamentary heater contained within an evacuated envelope, said envelope comprising an annular metallic electrodeterminal member having two oppositely disposed major sur faces, a first ceramic ring having a metallic'coating on the'outersur'face thereof, one end of said first ceramic ring being hermetically sealed to one of said major surfaces of said annular metallic member, a second ceramic ring surrounding said first ceramic ring in spaced relation thereto and having one end hermetically sealed to the same one of said major surfaces of said annular metallic member and on the flat portions of said major surface, said ceramic rings being in co-axial relationship to each other and to said annular metallic member, an elongated metallic rod Within and in spaced coaxial relation with said first ceramic ring and said annular metallic member, a hermetic seal between said rod and the inner surface of said first ceramic ring at an area spaced from the ends of said rod and said first ceramic ring, and a metallic electrode terminal ring sealed to the end portion of said second ceramic ring opposite from said annular metallic member, said filamentary heater being mounted on said rod, one end of said heater being electrically connected to said rod and the other end of said heater being electrically connected to said metallic coating on said first ceramic ring, said cathode being mounted on said first ceramic ring and electrically connected to said metallic coating, said metallic coating electrically connecting said heater and said cathode to said annular metallic member, and another one of said plurality of electrodes being electrically connected to said metallic terminal ring.

10. An electron tube comprising a plurality of electrodes including a cathode, an anode, a filamentary heater, and a control electrode contained within an evacuated envelope, said envelope comprising a first hollow cylindrical metallic member having a flat radially extending surface, a first ceramic ring, one end of said first ceramic ring being hermetically sealed to a portion of said radial surface of said first metallic member and said first ceramic ring having a metallic coating on the outer surface thereof electrically connected to said first metallic member, a second ceramic ring surrounding said first ceramic ring and having one end hermetically sealed to another portion of the same radial surface of said first metallic member, said ceramic rings being in co-axial relationship to each other and to said first metallic member, an elongated metallic rod extending co? axially Within said first metallic member and through said ceramic rings, a hermetic seal between said rod and a circumferential portion of the inner surface of said first ceramic ring, and a second hollow cylindrical metallic member surrounding said second ring and a portion of said first metallic member, said second metallic member having a portion of restrictive diameter hermetically sealed to said second ceramic ring at the end thereof opposite from said first metallic member, said filamentary heater being mounted on said rod, one end of said heater being electrically connected to said rod and the other end of said heater being electrically connected to said metallic coating on said first ceramic ring, said cathode being mounted on said first ceramic ring and electrically connected to said metallic coating thereon, and said control electrode being mounted on and electrically connected to said second metallic member, whereby said first and second metallic members and said metallic rod'may serve as electrical terminals for said tube.

References Cited in the file of this patent UNITED STATES PATENTS 2,629,066 Eitel et a1 Feb. 17, 1953 2,683,831 Skehan July 13, 1954 2,719,185 Sorg et :al. Sept. 27, 1955 2,720,608 Wihtol Oct. 11, 1955 2,722,624 Doolittle Nov. 1, 1955 2,819,421 Ringland et a1. Jan. 7, 1958 i ne-dd UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 2,939,032 May 31, 1960 Stanley Ru Jepson It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 6 line 8, after "relationship" strike out the comma; line 10, after "surface" insert a comma.

Signed and sealed this 22nd day of November 1960,

(SEAL) Attest:

KARL I-I. AXLINE ROBERT C. WATSON Attesting Ofiicer Commissioner of Patents