US2425127A - Apparatus for assembly of mounts - Google Patents

Description

Aug. 5, 1947.

E. W. SCHAF ER APPARATUS FOR ASSEMBLY OF MOUNTS Filed Dec. 20, 1943 Ill-lull ll ll l. .II. b J/ v Patented Aug. 5, 1947 APPARATUS FOR ASSEMBLX F MOUNTS Elwood W. Schafer, Millburn, N. J., assignor to National Union Radio Corporation, Newark,. N. J acorporati on of Delaware Application December 20, 1943, Serial No. ilfiflfifij 4 Claims. (01. 29- 2519) The-present invention relates to a'pparatus for the assembly of multiple electrodes into a unitary structure, commonly termed a mount, in the fabrication of discharge devices, particularly radio tubes.

The practice followed in building up-the mount structure of a multiple grid type radio tube requires at one stage of the-assembly the insertion into a supporting mica of one end of the electrodes, which may be a cathode, first'grid, second grid, third grid or beam plates and an anode, and then feeding the other ends of these electrodes individually into a second mica to make a unit assembly independent of the stem of the tube. All motion studies indicate that this second mica assembly or top mica threading has become a limiting operation in the high speed production of radio tubes. The correct breakdown of multiple operative mounting units is handicapped by the necessity of this second mica operation, and to obtain high group assembly production rates it is often necessary to employ two or three such operatives to keep up with preceding and following operations. This destroys the true line-of-production. and results in an even higher loss of efficiency than that due to the extra operatives.

As tube structures grow more complicated; as

more grids areused; and as tighter fits mustbe maintained between the grid legs and the mica holes toreduce microphonic effects the handicap imposed by the second mica assembly becomes more limiting. As greater group production rates are obtained by better motion study and breakdown of operations the more apparent becomes the effect of this one slow operation.

It is broadly an object of the present invention to provide a method of automatically aligning the projecting ends of work parts bythe use of magnetic means, whereby the time elementisreduced and the operation greatly simplified.

Another object of the invention is the provision of aligning and. holding means of a magnetic character, i. e., either a permanent magnet or an electromagnet, designed to contact the work parts-and hold the ends thereof in fixed position and relatively spaced, whereby the threading of supporting mica members over the projecting ends of the work parts is greatly facilitated.

Another object is the provision of a magnetic member terminating in a relatively thin blade designed to function as a gauge which may be moved into and out of engagement with the projecting ends of the work parts, whereby a precision operation necessary in making grid assembly is greatly facilitated.

Otherobjects relating to features of construc- Fig. '3 is an enlarged simplified diagrammatic '7 View, partly in section, showing particularly the,

grid elementsand including the top and bottom mica, constitutingthe supporting members of'the general mount assembly; and

Fig. 4 is an enlarged plan view, partly broken away, of the comlb-sha-ped' edge of the magnetic blade-member.

For a more detailed description, reference may be-had'to the drawings, more particularly-Figs.- 1 and'2; 'Inillustrating-m invention I have shown it embodied in an electromagnetically operated jig, but it will'be appreciated that the same principles would apply-ifa permanent magnetic structure-was used;

The jig member-may'consti'tute a super-structure supported from abase block I, having inserted therein a post 2 over which fits a collar 3, adjustable vertically on the post 2 by means of a thumb screw i. Carried at the top of the collar 3 isa supporting block 5. Mounted upon the upper face of theblock E'is ahead block member 6, which is seated in a cut-awayportion of the supporting blocki' and extends upwardly therefrom. The top surface of the head block 6 is provided with a counter-sunk'recess l, the general configuration of'which corresponds tothat of a mica 8, whichis commonly oblong in shape. Well pockets [6, formed vertical in the block 6, are in spaced relation and in alignment with one another. The purpose and/or function of this arrangement will hereinafter be more fully described.

The block 5 is drilled and keyed transversely near the basethereof to provide an opening for akey-pin 9, the fit between the pin 9 and its opening-being one of frictional engagement for means of adjustment. Carried upon the inner endof the pin 9 is a bracket; structure l0, including a crossbar member H which may be integral with an extending pole piece l2; the lower surface of which isinclined so as to form a sliding contact with a complementary inclined" surf-ace formed upon the upper opposing edge of the block 5. When these inclined surfaces are brought into engagement by manipulation of the cross-bar II, they constitute a firm support for the bracket structure I8, and also close the magnetic circuit by insuring sufiicient contact area between these parts, as will be more fully understood from the following description.

The electromagnet I3 may be of the usual construction comprising a spool having heads I4, between which is wound a coil (not shown) upon a core terminating at its upper end in a pole piece carrying a blade member I5. The blade member I5 tapers outwardly to form. a thin edge and is composed of magnetic material, such as iron. The front edge of the blade is provided with notches I'I formed in the magnetic material and these notches are alternated with sections I9 of nonmagnetic material, such as brass. The depth and width of the notches closely correspond to the diameter of the projecting legs I8 of the electrode members, and the spacing of the notches I'I conform to the center-to-center of the holes provided in the mica pieces, thus insuring a snug fit of the legs I 8 within the notches II, whereby said legs are held in more perfect alignment and spaced relation so that precision fitting may be obtained between the mica holes and the electrode legs. It will be appreciated by those skilled in the art that the tighter the fit between the holes in the mica and the projecting legs I8, there is a corresponding reduction in undesirable microphonic effects caused by a loose fit between these parts.

It will be noted that having the sides of the notches of non-magnetic material insures that the projecting ends I8 of the electrodes easily fall into the notches, and are retained in place by the magnetic material; further, that by regulating the length the non-magnetic material is inlaid or extends into the magnetic material, there is provided a coarse but simpl means for directing the effective magnetic force applied to the projecting electrode legs I8. It will also be appreciated some mount assemblies have projections on certain of the electrodes, as for example, the plate as shown in Fig. 2, which projections 2I are laterally spaced from the grid legs I 8, thus requiring a comparatively deep cut or insertion in the blade I5 to accommodate such laterally spaced projections 2|.

Variations of this character will occur for each type of grid assembly, and therefore a different jig set-up, by change in the blade I5, as well as change in the head block 6, will be required for changes in assembly structures, but the principle or mode of operation will be the same for the several grid assemblies.

Mounted in any suitable manner, as for example on the supporting block 5, is an electrical connector element 22 including a switch (not shown) and a pair of conductors 23 which carry the current for energizing the coil of the electromagnet, thus producing the magnetic field which magnetizes the blade I5. Normally the current is interrupted, but when desired, the circuit may be closed by manipulation of the control switch.

The method of assembly of the electrodes comprising a given mount, by the use of my jig, may be described as follows. By manipulating the cross-bar member I I, the electromagnet structure may be retracted or moved backwardly from the head block 6 as shown in Fig. 2. The reciprocal mounting of the pin 9 in the block 6 permits this adjustment. The mica 8,-used in this step of the assembly operations is usually designated as the first mica, is then dropped into the recess 1 by the operative. The placement of the first mica is such that the holes therein automatically fall into alignment with the well pockets I5. In the grid structure illustrated schematically in Fig. 3, the central electrode may be the sleeve of an indirectly heated type cathode. Adjacent to the cathode sleeve, and concentrically arranged therewith, may :be placed a plurality of grids, which may be designated generally as first, second, etc., grid, depending upon the grid structure undergoing assembly. On the outside of the grids may be inserted a pair of posts 24, to which may be secured the plate electrode, for example.

On the other hand, in the grid assembly shown in Figs. 1, 2, and 4, the cathode is of the directly heated type, which is inserted as a subsequent independent operation. The plate or anode which surrounds the grids, is provided with prongs 2| formed upon punched-out ears or extensions 28. To accommodate the projecting prong 2 I the central tooth of the blade member I5 is cut deeper, as shown particularly in Fig. 4.

Regardless of the type of assembly, the feature of importance is that all of the electrodes are manually loaded into the first mica, and upon the completion of the same, the magnetic structure is moved forward by operation of the crossbar II, so that the thin magnetic blade I5 is brought into operative position, i. e., with the notches II engaging the projecting legs I8 of the electrodes.

At this stage of the operation, the switch controlling the current through the electromagnet is actuated, thus completing the electric circuit which magnetizes the blade I5, resulting in the electrode legs I8 being automatically drawn into engagement with and firmly held within the notches II. Since the legs are now properly held in spaced relation to the holes in the mica 8, the top or second mica is easily threaded upon the legs I8 by merely dropping the mica thereover.

With the placement of the second mica over the legs I8 of the electrodes, the current producing the magnetic field may be interrupted, thus de-magnetizing the blade I5 or the permanent magnetic circuit maybe mechanically opened, by withdrawal of structure ID. This relieves the magnetic pull or attraction upon the projecting legs I8 and by manipulating the cross-bar I I, electromagnet I3 and component structure, may be moved rearwardly and out of engagement with the grid assembly. The operative is then free to remove th assembly from the head block 6. To facilitate this step in the operation, it will be noted that two opposing sides of the block 8 have been cut away to provide recesses 25, so that the fingers of the operative may be easily inserted underneath the first mica and the grid assembly withdrawn by an upper movement of the operatives hand.

It will be understood from the foregoing that for every change in the electrodes comprising a particular grid assembly, it will be necessary to change the head block 6 so as to accommodate the change in structure from one grid assembly to another. It may be noted at this point, that the depth of the several well pockets I8 is such that the projecting ends of the electrodes I 8 limit the distance said electrodes may doe inserted into the well pockets iii. In this manner, the distance the ends of the electrodes extend beyond the first or lower mica 8, is regulated at the time theeletrodes are dropped into the well pockets. With respect to regulating the amount of projection of the top of the legs I8 beyond the second mica, the same may be accomplished by regulating the height of the head block 6. That is to say, if the jig was previously adjusted for the fabrication of a miniature grid assembly, and it is desired to change to a larger type of grid assembly, it will not only be necessary to use a different arrangement of the well pockets IE, but also a shorter head block 6 since the distance between the block 5 and the edge of the blade [5 is fixed. Because of this requirement, the head block 6 is made demountable from the supporting block 5.

It may be observed at this oint that according to the construction and method of operation of my jig, it is no longer necessary to stagger the projecting ends of the electrodes so as to facilitate the insertion of these ends in the holes of the mica. That is to say, the support wires or posts for the electrodes may now be of equal length, thus saving in material and at the same time avoiding the inconvenience of making the electrode support wires of uneven lengths so as to produce a staggered relation therebetween.

As a matter of convenience for the operative, the grids super-structure is adjustable vertically on the post 2 so that by manipulating the thumb screw 4 the jig proper may be raised or lowered to bring the work parts on the most convenient level to suit a given operative.

I have found that by the use of my jig the operation of threading the top or second mica is greatly expedited and the operative performing this step in a line production unit can easily keep pace with the other operatives comprising the group.

Modifications and variations in the structure and/ or method disclosed herein will suggest themselves to those skilled in the art. For example, it is obvious that in the plac of using an electromagnet system, the blade [5 may be a permanent magnet. Further, in order to further facilitate the electrode legs l8 properly aligning themselves in the notches of the blade [5, the teeth of the comb portion of the blade may be tapered inwardly or slightly rounded off so that the openings of the notches I! are widened and act as guiding means for the legs [8 to enter the notches. The notches may also be made V-shaped. It is therefore desired to cover all such modifications as come within the scope of the appended claims.

What is claimed is:

1. In a mount assemsbly jig, a head block for supporting a first mica in a recess formed in the block, said head block being provided with well pockets in spaced relation with respect to the center-to-center spacing of holes in the mica,

said well pockets being adapted to receive the projecting ends of electrode elements and funcassembly thereof into a mount unit, electromag- -netic means associated with the head block including a core having a pol piece terminating in a blade member of magnetic material, the edge of said blade member having non-magnetic material alternated with the magnetic material, the magnetic portions of said edge being provided with notches, means for bringing the notches of the blade and the well pockets into alignment, and conducting means including a switch for the current producing a magnetic field which magnetizes the blade, whereby the projecting legs of the electrode elements are securely held in fixed position within the notches thus facilitating the threading f a second mica over said legs.

2. In a jig for assembling multiple electrode grid mounts, means for supporting one end of the electrodes in the same spaced relation with respect to holes of a first mica, means for aligning the opposite ends of the electrodes in correspondingly spaced relationship, and magnetic means for clamping the aligned free ends of the electrodes in said fixed relative position, whereby the threading of a second mica over the clamped ends of the electrodes is greatly facilitated.

3. The construction claimed in claim 2, wherein the magnetic means includes a blade member of magnetic material terminating in a relatively thin comb edge, the teeth of said comb being of non-magnetic material and separated from one another by notched out alternate portions of the magnetic material.

4. In a mount assembly jig, means for holding a perforated mica disc, said holding means being provided with well pockets correspondingly spaced with respect to the perforations of the mica and adapted to support the ends of electrodes projecting through said perforations, and magnetic means for clamping the unsupported ends of the electrodes in similarly spaced relationship to the supported ends of the electrodes, thus facilitating the threading of a second mica over the clamped ends of the electrodes.

ELWOOD W. SCHAFER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,109,659 Braden Sept, 8, 1914 1,956,840 Walmsley May 1, 1934 1,716,167 Grogan June 4, 1929

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