US 3311964 A
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April 4, 1967 A. A. M. HENDRIKS YETAL 3,311,964
METHOD OF MANUFACTURING A FRAME GRID Filed June 24, 1963 Man c 0/2 150 FRAME INVENTORS nommvus 4.x. usuonms MART/NUS A.M. BARKER AGENT United States Patent Office 3,311,964 Patented Apr. 4, 1967 3,311,964 METHGD F MANUFAC URIN G A FRAME GRID Adrianus Anthonius Maria Hendriks and Martinus Antonius Maria Bakker, Eindhoven, Netherlands, assignors to North American Philips Company, Inc., New York, N.Y., a corporation of Delaware Filed June 24, 1963, Ser. No. 239,842 Claims priority, application Netherlands, July 3, 1962, 280.941 4 Claims. (Cl. 29--25.14)
Our invention relates to a method of manufacturing frame grids for use in electron tubes.
Such a frame grid consists of a frame of molybdenum or of a Fe-Ni-Co-alloy on which tungsten wire is wound in one direction. Hitherto the turns of the wire were arranged on the frame by providing notches in which the wire was guided during the winding operation, after which the wire was pressed tightly in the notch. For the manufacture of frame grids having an extremely thin grid wire, for example having a diameter of to and a very small pitch, for example of 50 for onesided wound grids and of 100 for double-sided wound grids, this method is, however, quite unsuitable.
Frame grids having such an extremely thin grid wire may be used for example, in indicator tubes comprising ten cathodes in the form of the digits 0 to 9, an anode and one or more of such frame grids arranged between groups of the digital cathodes, or between each pair of cathodes. Since these digital cathodes may be caused to luminesce by a voltage applied thereto, the frame grids used in this case must be highly transparent.
Such frame grids may also be employed in amplifying tubes. With a view to a satisfying Ia-Vg characteristic curve of the tube, the pitch of the Winding must be at a minimum.
In one method for fixing the wire turns on the frame the latter is first coated with a phosphorus-containing nickel layer by means of an electroless nickel-plating bath consisting of an aqueous solution containing nickel ions and hypophosphite ions. Then the grid wire is wound on the frame and the assembly heated at a temperature between 700 C. and 800 C. In order to obtain a nickel layer having an adequately low melting point special precautions had to be taken, which consisted in that either any electroless nickel-plating bath for exhaustive nickel deposition or an electroless nickel-plating bath was used, to which a compound was added which formed complexes with nickel ion. In the former case a nickel layer is obtained having a phosphorus content increasing from the inner side to the outer side.
However, this method of fixing the turns resulted in a fairly high percentage of rejects. It was found that upon heating the frame wound with tungsten wire a brittle nickel-tungsten alloy was formed, so that the wires frequently broke when the nickel layer was well in the way of melting.
It is an object of our invention to provide an improved method using nickel to secure the turns to the frame of the grid. This and further objects of our invention will appear as the specification progresses.
The invention will be described with reference to the accompanying drawing in which FIG. 1 is a plan view of a vention; and
FIG. 2 is a detail view of the manner of attaching the grid wire to the frame.
Such a grid, a portion of which is shown in the accompanying drawing comprises nickel-coated rods 1 which are supported by cross-rods 2. A wire 3 is tautly wound about the rods 1, one end being clamped between crossrod 2 and rod 1 and the turns being secured to rod 1 grid according to the inby a layer of sintered nickel powder which fixedly positions the wires.
In accordance with the invention the frame is first coated galvanically or by chemical reduction with an adhering nickel layer, then wound with grid wire and then covered, at least at the place of the wires wound on the frame with a layer of nickel powder or nickel oxide powder and is heated in an inert atmosphere e.g., nitrogen or noble gases, or in the case of nickel oxide, in a reducing atmosphere, e.g., hydrogen, at a temperature between 700 C. and 800 C.
With this method the nickel powder is only sintered and fixedly surrounds the grid wires and, moreover, adheres satisfactorily to the nickel-plated frame surface.
Since the sintering to each other and the sintering of the powder to the nickel surface provide the adhesion, it is not necessary in this case for the nickel layer applied to the frame galvanically or by an electroless process to have a particularly low melting point. Any nickel layer applied galvanically or by chemical reduction is suitable for sintering the powdery nickel to it.
The powder layer of nickel or nickel oxide is prefer ably applied by means of a suspension.
Frame grids wound on one side may be obtained by winding grid wire on two joined frames and, subsequent to the fixation of the grid wires by the method according to the invention, by cutting or grinding the wires along the sides between the two frames.
While we have described our invention in connection with specific examples and applications thereof, other modifications will be readily apparent to those skilled in this art without departing from the spirit and scope thereof as defined in the appended claims.
What we claim is:
1. A method of manufacturing a grid comprising a wire wound on a frame, comprising the steps of applying an adherent layer of nickel to said frame, winding a wire on the so-coated frame, covering the wire where the wire is in contact with the frame with a material selected from the group consisting of nickel powder and nickel oxide powder, and heating between 700 and 800 C. the so-coated frame with the wire wound thereon in an atmosphere in which sintered nickel is formed wh ch fixedly surrounds the grid wires and adheres to the nickel layer covering the frame.
2. A method of manufacturing a grid comprising a Wire wound on a frame, comprising the steps of applying an adherent layer of nickel to said frame, winding a wire on the so-coated frame, applying nickel powder over the wire at the regions where the wire is in contact with the frame, and heating the so-coated frame with the wire wound thereon in an inert atmosphere at a temperature between 700 to 800 C. whereby sintered nickel is formed which fixedly surrounds the grid wires and adheres to the nickel layer covering the frame.
3. A method of manufacturing a grid comprising a wire wound on a frame, comprising the steps of applying an adherent layer of nickel to said frame, winding a wire on the so-c-oated frame, applying nickel oxide powder over the wire at the regions where the wire is in contact with the frame, and heating the so-coated frame with the wire wound thereon in a reducing atmosphere at a temperature between 700 to 800 C. whereby sintered nickel is formed which fixedly surrounds the grid wires and adheres to the nickel layer covering the frame.
4. A method of manufacturing a grid comprising a wire wound on a frame, comprising the steps of applying from an electroless nickel plating solution an adherent layer of nickel to said frame, winding a wire on the so-coated frame, applying over the wire at the regions where the wire is in contact with the frame with a ma- =5 4 terial selected from the group consisting of nickel pow- 2,945,295 7/1960 Feaster 29494 der and nickel oxide powder, and heating between 700 2,960,621 11/1960 Lane 313-350 and 800 C. the so-coated frame with the Wire Wound 3,130,757 4/1964 Schellack 14071.5 thereon in an atmosphere in which sintered nickel is 3,170,234 2/1965 Tarr 29501 formed which fixedly surrounds the grid Wires and ad- 5 heres t0 the nickel layer covering the frame. FOREIGN PATENTS 642,861 6/1962 Canada. References Cited by the Examiner UNITED STATES PATENTS JOHN F. CAMPBELL, Primary Examiner.
2,567,415 9/1951 Walsh 315-350 10 WILLIAMI. BROOKS, Examiner. 2,845,691 8/1958 Atherton 29 25.17