US1740159A - Variable condenser - Google Patents

Description

Dec. 17,A l929.` w. DUBILIER VARIABLE CONDENSER Filed Jan. 16. 1924 2 Sheets-Sheet nucl/1 Foz Dec. 17, 1929. w. DUBILIER VARIABLE CONDENSER Filed Jan. 16. 1924 2 Sheets-Sheet Patented Der. 17, i929 UNITED STATES PATENT oFFic-E Y WILLIAM nonnina, or NEW Yoax, ir.v Y.,

` ABSIGNOB TO DUBILIB COB- POBATION, 'A CORPORATION 0F DELAWARE VARIABLE coi'mENsEa- Applicatlon med January 18, 1924. Serial 111.680,54'.

My invention relates to condensers, and

more particularly to variable condensers.

Anobject of my invention 1s to provide a condenserin which the variations in set' tin may be exceedingly minute. I

nother object of my invention is to provide a condenser in which the .parts `are so supported that the danger o f injury'through .careless usage is almost entirely obviated.

necessary. This has beentrue for the reason that condensers of large enough capacity to be practical, register a largel change 1n capacity for a small cha-nge in setting.

through careless handling, the parts of variable condensers now in common use are sub- Moreover,

ject to derangement or` displacement, and consequently to injury. l Y l In my apparatus herein disclosed, I have rovided condenser elements, one,of which is iexible'and of spiral shape. The spiral shaped element is deformed to cause it to be progressivelylaid on the other element of y the condenser. VA relatively greatrlength of resilient element can be progressively moved into and out' o-engagement withl the fixed condenser element, with small change of lcapacity, since the spiral shape permits a great length of movable element to be comprised in a. small condenser. The great length of the kfiexible movable element permits minute variations to be made; change in capacity of 4 the device for any given length of movable yond its maximum values.-

velement brought` in contact with the fixed element vcan be made small. The ''exible spiral element of the condenser is spring Supa ported, thus obviating to a large degree possibilityl of injury to the condenser elements through attempts to adjust the condenser beand minimum capacity Figure 1 is a longitudinal sectional view i ltaken through the axis of the operatingfshaft on the line 1--1 of Fig. 2, looking in the direction of the arrows; Fig. 2 is abottom plan view of the condenser, artly in section, taken on the line 2-2 of 1g. 1, looking in the direction of the arrows;

Fig. is a top plan view of my condenser v partly in section, taken' on the line 3'3 of.

ig. 1, looking in the direction of the arrows; i t

Fig. 4 is .a lon itudinal sectional view of a modification o my condenser, such view.

- correspondin `to the view of my preferred form of con enser shown in Fig. 1.

Referring tothe drawings for a detailed description,y I have shown a condenser casing l.

orsupport 1 ofbakeliteforsome other suitable-insulating material, having a downwardly. depending annularlip 2, and provided with ian upstanding centrally .located protuberance 3. Against the upper inner wall 4 of the casing 1 is placed an annular strip of metal foil 5, :which comprises the metallic ortion of a fixed condenser element.'y The oil 5 is provided with a tab 6 which extends beyond thel periphery of the foil. Fitting over the tab 6 is a metallic holding washer v 7 and passing throughthe metallic holding washer 7 and the casing 1 is a binding ost j A8. A screw-threaded portion 9 of the bin in post extending above the casing l'has fitte thereover a washer 11', and over thewasher 11 a bolt 12. .The binding post 8 comprises one ofl the terminals of the condenser, and connection to that terminal may be made by lacing "a wire between-the washer 11 and) the nut 12'and tightening the nut 12. The foil 5 isf. preferably fastenedwithin a slight depression'13in the upper wall 4 of the casing 1, and the center of the foil 5 is cut away to leav a round aperture therein, as indicated at 1 Fastened over the foil 5 bis an insulatingv sheet 15, preferably of mica, which is attached to the foil 5 by some suitable adhesive. The

i mica strip 15 is cut away, as indicated at 16, lto permit the holding washer 7 to make electrical contact with the foil 5. 10

On the interior of the casing there is affixed at one end a spiral resilient metallic element 22. The end 23 at the outer diameterof this s irai element 22 is held in position by the binding post 17, and the spiral element 22 is intentioned away from the fixed element.

Passing through an apertureI 24 formed in the center of the spiral, approximately at the inner end 25, is a reciprocablel shaft 26. The shaft 26 has fitted over it a -supporting washer 27 prevented from downward movement on the shaft by means of av cotter pin 28. A helical spring 29 is mounted over the shaft- 26, and has its lower end 31 keyed into an aperture 32 in the holding washer 27.

The upper end 33 of the spring 29 is keyed in a hole 34 provided in the end 25 of the. b

resilient metallic movable element 22. The reciprocable shaft 26 passes upward through the protruding portion 3 of the casing 1,

through an aperture 35 formed in that portion of the casing. Screw-threads 36 are formed on shaft 26, which are adapted to enage with an internally screw-threaded coltr 37, keyed and firmly held within an interior aperture 38, formed in an operating knob 39 of bakelite, or some other insulating material.

The upper side of the protruding member 3 formed on the casing 1 is'formed with a horizontally extending annular flange 41-.

Resting on the u per surface of the member 3 is a friction was er 42 which is downwardly depressed, as indicated at 43, into a pocket i formed on the upper surface of the protrudven ing member 3. This prevents the friction washer 42 from rotating. The friction washer 42 is provided with a tab 44 which projects into a longitudinal slot 45 formed in the reci rocable shaft 26. The friction washer 42, tiirough the tab 44, prevents rot-ation of the reciprocable shaft 26. To hold the operating knob 39 in position, there is provided a U-shaped holding collar 46 which surrounds the annular flange 47 formed on the bottom of the operating knob 39. The collar is a split collar, and is deformed to fit over the fianges, after which the spring of the metal draws it in place, where it is held bv a bolt 48 and nut 49 that pass i through the ends 50.` The holding collar 46 does not fit so tightly as to prevent free rotation of the operating knob 39, whose rotation electhecondenser beyond its carries with it the internally threaded member 37, adapted to turn with the operating knob 39.

Rotation of the operating knob 39 causes the reciprocable shaft 26 either to-be drawn up into the knob, or pushed downwardly, del pending on the direction of rotation. The

shaft 26 is prevented from rotation by means of the tab 44 formed on the friction washer 42. The movement of the shaft carries with it the spring 29 )and consequently the free end .of the spiral member 22. The spiral member 22 is subjected to a picking up and laying down action, on the fixed element of the condenser, comprising the foil 5 covered by the insulating mica sheet 15.

The capacity of the condenser may be sub- .ting of delicate adjustment is of peculiar advantage in radio communication. Moreover, y reason of the spring connections between the reciprocable shaft 26, and` the movable member of the condenser, attempts to adjust maximum and minimum values will accomplish no harm, since the sprin'gr connections prevent injury to the delicate parts.

Referring to Fig. 4, I have shown a different modification of my invention embod ing the same principle of operation. In the ferm shown in Fig. 4, the spiral member 22 is in inverse position, and is adapted to be laid down upon the fixed member beginning at its small diameter and progressing to its lar er diameter. In this form of device, the reciprocable shaft 26 is provided at its lower end with a screw-threaded portion 51. Threaded over the shaft 26 isa supporting plate 52, preferably of bakelite, or some other suitable insulating material. The plate 52 rests on an annular flange 53 formed on a hollowed bolt member 54, whose interior threads engage with the threads 51 of the reciprocable shaft 26. In the position of maximum capacity,when the plate 52 compresses all of the spiral 22 against the fixed element of the condenser, the compressed spring 29 is housed in the hollowed bolt member 54. The end 25 of the spiral resilient movable member 22 is fastened by means of screws 55 against a conductor str1p 56 positioned against the center of the upper wall 4 of the casing 1. The conductor strip 56 passes upwardly and outwardly through the aperture 57 formed in the casing 1, and then along the casing. The bindmovable member may be made throu i h binding post 17 by loosening the nut 21 an clamp- -mentis given a slight offset, as indicated at' 58, to prevent injury to the mica or the foil of the fixed condenser element in the operation of the condenser. This offset insures that the mica and foil will not be subjected to a pinchin action at their edges. If such pinching action should take place, however, there would be slight danger of short-circuit ing, by reason of the fact that in all ofA these forms of condenser, the fixed element is composed of a strip of foilwhose inner and outer eldges are overlapped by the insulating mica s eet. Y

The operation of the form of condenser `-shown in Fig. 4 is quite Asimilar to my preferred form illustrated in Figs. 1 to 3 inclu sive. -In the form of condenser shown in Fig. 4, the laying down operation begins at the'small diameter of Ithe spiral, in other words, near the center, and is progressively continued to the larger or outer diameter of the spiral.

While I have shown and described the preferred embodiment of my invention, I wish it to be understoodthat I do not confine my self to the precise details of construction herein set forth, by way of illustration, as it is apparent that many changes and variations may be made therein, b those skilled in the art, without departing rom the spirit of the invention, or exceeding the scope of the appended claims.A

I claim 1. A variable condenser comprising, a support, a fixed element carried by the support, a rotatable screw-threaded member, a spiral movable element, 4a screw-threaded shaft with a channel therein whose threads engage the threads of the screw-threaded-member, a

washer fixed to the support between theI screw-threaded member andthe support, a

"lug on the washer fittinginto the channel of the shaft, and means operated by the reciprol cation of the shaft to progressively press the spiral element against the fixed element.

2. A variable condenser comprising a fixed -`elementanda movable element separated by insulation, the movable element having-the form of a flat spiral, and means for deforming said spiral element to vary the capacity of the condenser. 1

3. A variable condenser comprising a support, a fixed element attached thereto, a resilient element in the form of a fiat spiral fas-l tened at one end to said support and having its free end spaced from the fixed element, dielectric material between said elements, and

means engaging the free end of the spiral element to cause the same tovapproach and recede from said fixed element in order to vary the capacity of the condenser. v

4. Al varlable condenser comprising a fixed element, a movable flexible element in the form of a spiral having a plurality'of convolutions, said spiral having a fixed end and a free end,'dielectric material between said elements, and means including a 'spring engag-v ing the free end of said spi-ral for causing its surface to progressively approach and recede from the fixed element.

5. A variable condenser comprising'a fixed element, a resilient element inthe form of a spiral having a plurality of convolutions, insulation between said elements, and a screw cooperating with the spiral element to cause it to approach and recede from the fixed element in order to vary the capacity of the condenser. i

6. A variable condenser comprising a support, a fixed element attached thereto, a resilient element in the form of a -flat spiral fastened at its larger end to saidA support and having its smaller end spaced from the fixed element, dielectric material between said elements, and means engaging the smaller end of said spiral to cause its surface to progressively approach and recede from the fixed element.

In testimony whereof I aflix my signature. WILLIAM DUBILIER.

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